Method for reactivation of platinum group metal catalyst with aqueous alkaline and/or reducing solutions

ABSTRACT

A method for reactivation of a platinum group metal catalyst which comprises treating the platinum group metal catalyst lowered in catalytic activity as the result of having been used for the catalytic reaction of hydrocarbons optionally containing an oxygen atom with at least one agent selected from an inorganic alkaline substance and a reducing substance in an aqueous medium.

This is a continuation-in-part application of our copending applicationSer. No. 861,521 filed Dec. 16, 1977 now U.S. Pat. No. 4,147,660, issuedApr. 3, 1979.

The present invention relates to a method for reactivation of a platinumgroup metal catalyst. More particularly, it relates to a method forreactivation of a platinum group metal catalyst lowered in catalyticactivity as the result of having been used for the catalytic reaction ofhydrocarbons optionally containing an oxygen atom.

Conventional catalysts of this type which have been used in thecatalytic reaction of hydrocarbons optionally containing an oxygen atom,such as in the steam-reforming of hydrocarbons, hydro-cracking ofhydrocarbons, partial oxidation of hydrocarbons and steam-reforming ofalkanols, include base metal (e.g. Fe, Ni, Co) catalysts and noble metal(e.g. Pt, Pd, Ru) catalysts. In comparison with the base metal catalysts(particularly nickel catalysts), the noble metal catalysts (particularlyplatinum group metal catalysts) possess certain advantages as, forinstance, resistance to the deposition of carbonaceous materials thereonand maintenance of high catalytic activity with use in small amounts.However, due to the expensiveness of the noble metal catalysts, thepractical considerations have been concentrated in the use of the basemetal catalysts. In order to overcome this shortcoming, attempts havebeen made to reactivate noble metal catalysts lowered in the catalyticactivity so as to enable their reuse. Typical conventional proceduresfor such reactivation include treatment with hydrogen, steam or oxygen,and in fact, such procedures are quite effective in the elimination ofcertain poisonous materials in addition to the carbonaceous materialsdeposited on the catalysts. However, the recovery of the catalyticactivity provided by these procedures is frequently not satisfactory.

In general, catalytic reactions of hydrocarbons optionally containing anoxygen atom in the presence of a platinum group metal catalyst result indeposition of various materials such as carbonaceous materials andsulfurous materials on the catalyst particles. In addition, thesecatalytic reactions often result in a sintering of the catalystparticles causing their mutual cohesion, whereby the particle size ofthe catalyst enlarged and the dispersibility of the catalystconsequently lowered. Further, the physical and chemical constitutionsand behaviors of the catalysts may be gradually changed during thecatalytic reactions. Due to these and other factors which are stillunclear, the catalytic activity of the catalyst is lowered during thecourse of the catalytic reaction. In order for recovery of the catalyticactivity to reach a practically satisfactory level, it is necessary tosubstantially reduce or eliminate these adverse factors.

As the result of extensive study, it has now been found that treatmentof platinum group metal catalysts lowered in catalytic activity bycontact with at least one agent selected from an inorganic alkalinesubstance and a reducing substance in an aqueous medium provides aneffective recovery of the catalytic activity. It has also been foundthat the combination of treatments with both an inorganic alkalinesubstance in an aqueous medium and a reducing substance in an aqueousmedium is particularly effective for accomplishment of the reactivation.It has further been found that the reactivation effected by thetreatment with the inorganic alkaline substance and/or the reducingsubtance can be more assured by treating the catalyst lowered incatalytic activity with hydrogen, steam or oxygen before or after thetreatment with the inorganic alkaline substance and/or the reducingsubstance.

It may be noted that conventional treatment with hydrogen, steam oroxygen is effective for the removal of carbonaceous materials depositedon the catalyst but not for the elimination of sulfurous materials. Onthe other hand, treatment with an inorganic alkaline substance or areducing substance is highly effective for the removal of sulfurousmaterials though the effect of elimination of carbonaceous materials maynot be as high as obtained by conventional treatment with hydrogen,steam or oxygen. Particularly notable is the fact that while theconventional treatment has almost no effect on the recovery of thelowered catalytic activity, treatment with an inorganic alkalinesubstance or a reducing substance has a surprisingly significant effect.

According to the present invention, the reactivation of a platinum groupmetal catalyst lowered in the catalytic activity is carried out bytreatment of the catalyst with at least one inorganic alkaline substanceor at least one reducing substance or both, in an aqueous medium.

The platinum group metal catalyst to be subjected to the treatment inthe present invention may be the one which comprises a platinum groupmetal such as ruthenium, rhodium, palladium, osmium, iridium or platinumas the catalyst component deposited on a carrier material such asalumina, magnesia, zirconia, titania, silica, silica-alumina,silica-magnesia, alumina-magnesia or carbon and lowered in catalyticactivity as the result of having been used for the catalytic reaction ofhydrocarbons optionally containing an oxygen atom. In addition to thesaid essential catalyst component, the platinum group metal catalyst maycomprise any additive which does not materially afford any unfavorableinfluence thereon. Examples of the additive include any material knownas the so-called "co-catalyst" such as alkali metals, alkaline earthmetals, iron, copper, nickel, cobalt, chromium, tungsten, manganese ormolybdenum. The term "hydrocarbons optionally containing an oxygen atom"hereinabove used is intended to mean organic compounds consisting ofcarbon atoms and hydrogen atoms or of carbon atoms, hydrogen atoms andoxygen atoms, and their examples include aliphatic hydrocarbons,aromatic hydrocarbons, naphthenic hydrocarbons, alkanols, alkanones,etc. Examples of the catalytic reaction are steam-reforming ofhydrocarbons, hydro-cracking of hydrocarbons, partial oxidation ofhydrocarbons, steam-reforming of alkanols, etc.

The inorganic alkaline substance may be an inorganic alkaline compoundcontaining at least one alkali metal or alkaline earth metal. Examplesof the alkali metals and the alkaline earth metals are sodium,potassium, calcium, magnesium, barium, strontium, etc. Preferredexamples of the inorganic alkaline compounds containing these alkalimetals and alkaline earth metals are hydroxides, carbonates, nitrates,sulfates, etc. or mixtures thereof. The concentration of the inorganicalkaline substance in the aqueous medium may be varied depending uponthe amount of the catalyst component deposited on the carrier material,the degree of lowered catalytic activity, the temperature and pressureat which the reactivation treatment is carried out and the like. Ingeneral, however, the concentration is usually from about 0.001 to 10 N,preferably from about 0.001 to 5 N.

As the reducing substance, there may be employed normally water-solubleor water-dispersible reducing substances such as hydrazine,formaldehyde, sodium borohydride, lithium aluminum hydride, sodiumtartrate, potassium tartrate, sodium potassium tartrate, calciumtartrate, sodium hydrogen tartrate, sodium formate, potassium formate,calcium formate, glucose, etc. or mixtures thereof. The concentration ofthe reducing substance in the aqueous medium depends on the amount ofthe catalyst component deposited on the carrier material, the degree oflowered catalytic activity, the temperature and pressure employed in thereactivation treatment, etc. Normally it falls in the range of about0.01% to 10% by weight.

Even when the catalyst lowered in catalytic activity is treated solelywith the inorganic alkaline substance or the reducing substance,appreciable elimination of sulfurous materials deposited on the catalystand considerable recovery of the catalytic activity can be attained bychoosing appropriate conditions for the treatment. In general, however,the treatment is preferably carried out in two separate steps, i.e. bytreatment with the inorganic alkaline substance and then treatment withthe reducing substance, or vice versa. When desired, such as two steptreatment may be repeatedly applied until a satisfactory recovery of thecatalytic activity is achieved, though a single application of two steptreatment is usually sufficient.

The treatment with the inoganic alkaline substance is usually effectedat room temperature (i.e. about 5° to 30° C.) or while heating underatmospheric pressure or an elevated pressure. Howver, it can be widelyvaried depending on the extent of lowered catalytic activity, thecomposition of the catalyst, the kind of the inorganic alkalinesubstance employed, etc. In general, a higher temperature affords abetter result, but too high a temperature should be avoided since thecarrier material may be unfavorably dissolved. Thus, the temperature isusually from about 5° to 250° C., preferably from about 50° to 200° C.The pressure may be appropriately selected so as to maintain the systemfor treatment in a liquid state, and such pressure do not usually exceed50 kg/cm².

Treatment with the reducing substance may be carried out at atemperature from room temperature to the decomposition temperature ofthe reducing substance under atmospheric pressure or at an elevatedpressure. Although the temperature is considerably affected by variousfactors such as the extent to which the catalytic activity is lowered,the composition of the catalyst and the kind of the reducing substance,the temperature is ordinarily between room temperature and about 250° C.insofar as the reducing substance is not decomposed. The pressure may beappropriately selected so as to keep the system in a liquid state and isnormally not higher than 50 kg/cm².

When combined two step treatments with the inorganic alkaline substanceand with the reducing substance are effected in this order or viceversa, these may be performed with or without intervention ofwater-washing and/or drying between them.

The treatment(s) with the inorganic alkaline substance and/or with thereducing substance may be effected until a satisfactory recovery of thecatalytic activity is attained. Usually, treatment(s) effected so as toeliminate not less than about 40% of carbonaceous materials and not lessthan about 70% of sulfurous materials deposited on the catalyst willachieve the satisfactory recovery of the catalytic activity. The contactor treating time employed will vary depending upon many factors such aswhether one or two step treatments are used, the degree of recovery ofcatalytic activity desired, etc. Usually a treating time of severalminutes to several tens hours (e.g. 3 minutes to 80 hours) is generallysufficient to achieve the aforementioned satisfactory recovery ofcatalytic activity. However, as stated above, the deterioration of thecatalytic activity is caused not only by deposition of carbonaceousand/or sulfurous materials but also by other unclear factors, andtherefore the elimination of the said deposited materials may not alwaysbe sufficient for recovery of the catalytic activity. If necessary,therefore, the said treatment(s) with the inorganic alkaline substanceand/or with the reducing substance may be carried out in combinationwith any conventional reactivation treatment. For instance, thetreatment of the catalyst with hydrogen, steam or oxygen may be effectedprior to, between or subsequent to the treatment(s) with the inorganicalkaline substance and/or with the reducing substance.

Examples of usable gases for the conventional reactivation treatment arehydrogen, oxygen, steam, a mixture of hydrogen and steam, a mixture ofoxygen and steam, etc. These gases may be optionally diluted with anyother inert gas such as nitrogen, helium or argon. Particularlypreferred are (1) hydrogen, (2) a mixture of hydrogen and steam having ahydrogen content of not less than about 30 mol%, (3) a mixture of steamand a gaseous diluent having a steam content of not less than about 30mol %, (4) a mixture of oxygen and a gaseous diluent having an oxygencontent of not less than about 0.5% by volume, (5) a mixture of oxygen,steam and a gaseous diluent having an oxygen content of not less thanabout 0.5% by volume and a steam content of not less than about 30% byvolume, etc.

The conditions for treatment with the said gases depend on the amount ofthe catalyst component deposited on the carrier material, the depositedamount of poisonous materials (particularly carbonaceous materials), theconcentration of the active gases, the kind of other treatmentprocedures employed, etc. Usually a temperature of about 350° to 750° C.and a pressure of about 1 to 50 atm. (absolute) are adopted. Thetreatment may be continued until the deposited amount of poisonousmaterials, particularly carbonaceous materials, is appreciablydecreased. When the deposited amount of carbonaceous materials isrelatively large, the generation of heat occurs sometimes. In such case,the oxygen content in the treating gases may be decreased or the use ofthe treating gases containing no oxygen is preferred.

After the finalization of the treatment(s) as explained above, theresulting catalyst may be washed with water and/or dried. Particularly,when the final step is the treatment with the inorganic alkalinesubstance or the reducing agent in an aqueous medium, water washing anddrying are favorable.

As stated above, the thus reactivated catalyst is satisfactorilyrecovered in catalytic activity. Even when the catalyst is severelypoisoned and its catalytic activity is extremely lowered, the repeatedapplication of the above treatment(s) enables the satisfactory recoveryof catalytic activity nearly equal to that of a freshly preparedcatalyst. Further, when the once reactivated catalyst is lowered againin the catalytic activity, the repeated application of the abovetreatment(s) will reactivate it. Thus, the present invention is quiteadvantageous in making it possible to use an expensive platinum groupmetal catalyst repeatedly.

Practical and presently preferred embodiments of the present inventionare illustratively shown in the following Examples wherein part(s) and %are by weight unless otherwise indicated. The amount of the catalystrequired for reaction indicates a minimum amount of the catalystrequired for showing a catalytic activity for reaction.

EXAMPLE 1

A catalyst comprising 2.0% of ruthenium and 0.1% of chromium oxidedeposited on spheroidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₁ ") (325 ml)was charged into a tubular reactor of 1 inch in diameter, and a gaseousmixture comprising naphtha (content of sulfur, 2 ppm; final boilingpoint, 168° C.), steam, hydrogen, methane and carbon oxides was fedtherein to effect continuously steam-reforming reaction for 1500 hoursunder the following conditions:

Temperature of reactor: inlet, 450° C., outlet, 524° C.;

Space velocity: 2000 (l/hr);

Ratio of steam/hydrocarbon: 0.9 (number of oxygen atoms per one carbonatom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 1500 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₁ ") was treated under the conditions as shown in Table 1 forreactivation. The reactivated catalyst was reused in steam-reformingreaction under the same conditions as mentioned above. The results areshown in Table 1.

As seen from Table 1, the reactivation treatment with hydrogen isextremely effective for elimination of carbonaceous materials, butremoval of sulfurous materials is insufficient and the dispersibilitycan be hardly recovered so that recovery of the catalytic activity isscarcely observed (Catalysts C₁ -1 and C₁ -2). In the case of treatmentwith an inorganic alkaline substance, elimination of sulfurous materialsand recovery of the dispersibility as well as recovery of the catalyticactivity are good.

    Table 1      Reactivated Catalyst  A.sub.1 B.sub.1 C.sub.1 -1 C .sub.1 -2 D.sub.1 -1 D     .sub.1 -2 D.sub.1 -3 D.sub.1 -4 D.sub.1 -5 D.sub.1 -6 D.sub.1 -7 D.sub.1     -8 D.sub.1 -9 D.sub.1 -10 D.sub.1 -11 D.sub.1      -12                          Condi- Reactivating -- -- H.sub.2 O.sub.2     :N.sub.2 0.375N 0.375N 0.375N 1.0N 5.0N 0.375N 0.375N 0.375N 0.375N     0.375N 0.375N 0.001N tions agent*)    (=21: NaOH NaOH NaOH NaOH NaOH     Na.sub.2 CO.sub.3 KOH Ba(OH).sub.2 Sr(OH).sub.2 NaOH NaOH NaOH of     79     by treat-     volume) ment for Temper- -- -- 650 500 50 70 100 100 70     100 100 100 100 148 205 100 reacti- ature (°C.) vation  Pressure     -- -- 6.0 6.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 5.0 20.0 1.0  (ata)     Time (hrs) -- -- 12 5 6.0 3.0 1.5 0.75 0.5 3.0 3.0 3.0 3.0 1.0 0.5 10.0     Post-treat- -- -- -- -- Water washing: 100° C., 2 hrs. ment     Drying: 100° C., 16 hrs. Elimina- Carbo- -- -- 100 100 41 46 55     54 59 54 52 50 48 56 58 40 tion per- naceous centage materials of     poisonous Sulfurous -- -- 33 40 78 84 95 97 100 93 90 87 87 100 100 80     materials materials (%) Specific surface area 43 20 19 17 28 30 35 37 37 3     6 35 33 32 34 37 30    (m.sup.2 /g-Ru) Amount of catalyst 52.5 -- -- --     85 68 63 63 61 64 64 66 68 63 60 69 required for reac- tion (ml)     *In case of Catalysts C.sub.1 -1 and C.sub.1 -2, the treatment was carrie     out with a space velocity of 2500 (1/hr).

EXAMPLE 2

A catalyst comprising 0.3% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter as a carrier material (1000 ml)was charged into a tubular reactor of 1 inch in diameter, and naphtha(final boiling point, 108° C.) and hydrogen were fed therein to effectcontinuously hydro-cracking reaction under the following conditions:

Temperature of reactor at inlet: 265° C;

Pressure: 46 atm. (absolute);

Ratio of hydrogen/hydrocarbon: 1.20 (by mol)

Mass velocity: 500 kg-mol/m². hr

The conversion of hydrogen at the initial stage was 82%, and thecatalytic activity was materially decreased after about 200 hours. Theresultant catalyst was heated in a 0.375 N aqueous solution of sodiumhydroxide at 100° C. for 3 hours, washed with water at 100° C. for 2hours and then dried at 100° C. for 16 hours. The thus reactivatedcatalyst was reused for hydro-cracking under the same conditions asabove, whereby a conversion of hydrogen of 80% was observed.

EXAMPLE 3

A catalyst comprising 2.6% of ruthenium and 0.1% of chromium oxidedeposited on spheroidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₂ ") (325 ml)was charged into a tubular reactor of 1 inch in diameter, and a gaseousmixture comprising naphtha (content of sulfur, 2 ppm; final boilingpoint, 168° C.), steam, hydrogen, methane and carbon oxides was fedtherein to effect continuously steam-reforming reaction for 2400 hoursunder the following conditions:

Temperature of reactor: inlet, 400° C., outlet, 517° C;

Space velocity: 1500 (l/hr);

Ratio of steam/hydrocarbon: 0.7 (number of oxygen atoms per one carbonatom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 2400 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₂ ") was treated under the conditions as shown in Table 2 forreactivation. The reactivated catalyst was reused in steam-reformingreaction under the same conditions as mentioned above. The results areshown in Table 2.

As seen from Table 2, the reactivation treatment with hydrogen isextremely effective for elimination of carbonaceous materials, butremoval of sulfurous materials is insufficient and the dispersibilitycan be hardly recovered so that recovery of the catalytic activity isscarcely observed (Catalyst C₂). In the case of treatment with aninorganic alkaline substance at room temperature, elimination ofsulfurous materials and recovery of the dispersibility are relativelygood when the treating time is long, but the recovery of the catalyticactivity is insufficient (Catalysts D₂ -1 and D₂ -2). The treatment withan inorganic alkaline substance under heating is proved to be effectivefor recovery of the catalytic activity (Catalysts D₂ -3to D₂ -5). In thetreatment with a reducing substance, elimination of sulfurous materialis good, but removal of carbonaceous materials is hardly attained. Thereis a tendency to recovery of the catalytic activity (Catalysts D₂ -6 toD₂ -13).

    Table 2      Reactivated Catalyst  A.sub.2 B.sub.2 C.sub.2 D.sub.2 -1 D.sub.1 -2     D.sub.1 -3 D.sub.1 -4 D.sub.2 -5 D.sub.2 -6 D.sub.2 -7 D.sub.2 -8     D.sub.2 -9 D.sub.2 -10 D.sub.2 -11 D.sub.2 -12 D.sub.2      -13                 Condi- Reactivating -- -- H.sub.2 0.375N 0.375N     0.375N 0.375N 0.375N 0.4% 0.3% 0.7% 2.0% 0.3% 1.0% 1.0% 1.0% tions     agent*    NaOH NaOH NaOH NaOH NaOH Hydra- Lithium Sodium Sodium Glucose     Hydra- Formal- Sodium of          zine aluminum tart- formate  zine     dehyde boro- treat-           hydride rate     hydride ment for Temper-     -- -- 650 30 30 50 100 148 20 20 20 20 60 60 60 reacti- ature (°C.     ) vation  Pressure -- -- 6.0 1.0 1.0 1.0 1.0 5.0 1.0 1.0 1.0 1.0 1.0 1.0     1.0 1.0  (ata)  Time (hrs) -- -- 12.0 3.0 10.0 6.0 3.0 1.0 3.0 3.0 3.0     3.0 3.0 3.0 3.0 3.0 Post-treat- -- -- -- Water washing: 100° C.,     2 hrs. Water washing: Water washing: 75° C., 3 hrs. ment     Drying: 100° C., 16 hrs. 75°      C., 3 hrs. Drying: 100° C., 16 hrs.      Drying: 100° C.,          16 hrs. Elimina- Carbo- -- -- 100 12 41 43 52 56 0 0 0 0 0 0 0 0     tion per- naceous centage materials of poisonous Sulfurous -- -- 31 32     72 78 90 100 68 49 46 53 49 90 67 88 (%) Specific surface area 43 71 17     21 27 28 34 35 21  23 23 23 23 23 23 23    (m.sup.2 /g-Ru) Amount of     catalyst 92 -- -- -- -- 147 110 106 276 270 272 272 276 266 270 276     required for reac- tion (ml)     *In case of Catalyst C.sub.2, the treatment was carried out with a space     velocity of 2500 (1/hr).

EXAMPLE 4

The reactivated catalysts as obtained in Example 3 (Catalysts D₂ -1 toD₂ -4 and D₂ -6 to D₂ -12) were each subjected to further treatment forreactivation under the conditions as shown in Table 3. The thusreactivated catalysts were each reused for continuous steam-reformingunder the same conditions as shown in Example 3. The results are shownin Table 3.

As seen from Table 3, the catalysts (E₃ -1 to E₃ -20) reactivated in twosteps are much more recovered in catalytic activity than the catalysts(D₂ -1 to D₂ -4 and D₂ -6 to D₂ -12) reactivated in one step.

    Table 3      Catalyst E.sub.3 -1 E.sub.3 -2 E.sub.3 -3 E.sub.3 -4 E.sub.3 -5 E.sub.3     -6 E.sub.3 -7 E.sub.3 -8 E.sub.3 -9 E.sub.3 -10 E.sub.3 -11 E.sub.3 -12     E.sub.3 -13 E.sub.3 -14 E.sub.3 -15 E.sub.3 -16 E.sub.3 -17 E.sub.3 -18     E.sub.3 -19 E.sub.3 -20 Catalyst used D.sub.2 -1 D.sub.2 -2 D.sub.2 -3     D.sub.2 -3 D.sub.2 -4 D.sub.2 -4 D.sub.2 -6 D.sub.2 -6 D.sub.2 -11     D.sub.2 -12 D.sub.2 -1 D.sub.2 -2 D.sub.2 -3 D.sub.2 -3 D.sub.2 -4     D.sub.2 -4 D.sub.2 -7 D.sub.2 -8 D.sub.2 -9 D.sub.2      -10                    Condi- Reacti- 1.0% 0.4% 0.4% 0.5% 0.4% 0.3%     0.375N 0.375N 0.375N 0.375N 0.3% 0.3% 0.7% 2.0% 0.3% 0.3% 0.375N 0.1N     0.375N 0.375N tions vating Hydra- Hydra- Hydra- Formal- Hydra- Sodium     NaOH NaOH NaOH NaOH Lithium Lithium Sodium Sodium Lithium Glu- NaOH NaOH     NaOH NaOH of agent zine zine zine dehyde zine boro-     alum- alum-     tart- formate alum- cose treat-       hy-     inum inum rate  inum ment          dride     hydride hydride   hydride for Temper- 60 20 20 20 20 20     50 100 100 80 20 20 20 20 20 20 50 100 100 80 reacti- ature vation     (°C.)  Pressure 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0     1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  (ata)  Time 3.0 3.0 3.0 3.0 3.0 3.0 6.0     3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 6.0 3.0 1.5 3.0  (hrs) Post- Water     washing: 75° C., 3 hrs. Water washing: 100° C., 2 hrs.     Water washing: 75° C., 3 hrs. Water washing: 100° C., 2     hrs. treat- Drying: 100° C., 16 hrs. Drying: 100° C., 16     hrs. Drying: 100° C., 16 hrs. Drying: 100° C., 16 hrs.     ment Elimina- Carbo- 12 41 43 43 52 52 43 54 53 47 12 41 43 43 52 52 43     44 46 47 tion per- naceous centage materials of poisonous Sulfurous 89     91 93 93 97 95 91 97 95 89 66 86 89 90 95 95 89 88 93 92 materials     materials (%) Specific surface area 34 36 36 36 40 40 35 39 41 39 31 36     37 37 41 40 38 37 37 37    (m.sup.2 /g-Ru) Amount of catalyst 108 110     102 106 95 98 102 95 93 95 126 106 100 100 94 95 98 100 100 100 required     for reac- tion (ml)

EXAMPLE 5

The reactivated catalyst obtained in Example 3 (Catalyst D₂ -3) wastreated with a 0.4% aqueous solution of hydrazine at 20° C. under 1 atm.(absolute) for 3 hours, washed with water at 75° C. for 3 hours anddried at 100° C. for 16 hours. Then, the resulting catalyst was againsubjected to treatment with a 0.375 N aqueous solution of sodiumhydroxide at 50° C. under 1 atm. (absolute) for 6 hours and treatmentwith a 0.4l % aqueous solution of hydrazine at 20° C. under 1 atm.(absolute) for 3 hours, followed by washing with water at 75° C. for 3hours and drying at 100° C. for 16 hours. The thus reactivated catalystwas used for steam-reforming under the same conditions as stated inExample 3. The results are as follows: elimination percentage ofpoisonous materials: carbonaceous materials, 75%; sulfurous material,100%. Specific surface area: 42 m² /g-Ru. Amount of catalyst requiredfor reaction: 93 ml.

As seen from the above results, the repeating treatments with aninorganic alkaline substance and with a reducing substance are quiteeffective for reactivation of the catalyst.

EXAMPLE 6

The reactivated catalyst obtained in Example 3 (Catalyst D₂ -3) wastreated with a 0.7% aqueous solution of sodium tartrate at 20° C. under1 atm. (absolute) for 3 hours, washed with water at 75° C. for 3 hoursand dried at 100° C. for 16 hours. Then, the resulting catalyst wasagain subjected to treatment with a 0.375 N aqueous solution of sodiumhydroxide at 50° C. under 1 atm. (absolute) for 6 hours and treatmentwith a 0.7% aqueous solution of sodium tartrate at 20° C. under 1 atm.(absolute) for 3 hours, followed by washing with water at 75° C. for 3hours and drying at 100° C. for 16 hours. The thus reactivated catalystwas used for steam-reforming under the same conditions as stated inExample 3. The results are as follows: elimination percentage ofpoisonous materials: carbonaceous materials, 70%; sulfurous material,100%. Specific surface area: 42 m² /g-Ru. Amount of catalyst requiredfor reaction: 93 ml.

As seen from the above results, the repeating treatments with aninorganic alkaline substance and with a reducing substance are quiteeffective for reactivation of the catalyst.

EXAMPLE 7

A catalyst comprising 3.8% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter (hereinafter referred to as"Catalyst A₄ ") (325 ml) was charged into a tubular reactor of 1 inch indiameter, and naphtha (content of sulfur, 2 ppm; final boiling point,220° C.) and steam were fed therein to effect continuouslysteam-reforming reaction from 750 hours under the following conditions:

Temperature of reactor: inlet, 510° C., outlet, 518° C.;

Space velocity: 2000 (l/hr);

Ratio of steam/hydrocarbon: 1.9 (number of oxygen atoms per one carbonatom in the feeding gaseous materials);

Pressure: 13 atm. (absolute)

After 750 hours, the catalyst (hereinafter referred to as "Catalyst B₄") was treated under the same conditions as shown in Table 4 forreactivation. The reactivated catalyst was reused in steam-reformingreaction under the same conditions as mentioned above. The results areshown in Table 4.

As seen from Table 4, treatment with an inorganic alkaline substanceshows recovery of the catalytic activity, and treatment with a reducingsubstance shows a tendency to recovery of the catalytic activity.However, when the catalyst is severely polluted, an elevated temperatureis necessary for satisfactory recovery of the catalytic activity bytreatment with an inorganic alkaline substance.

    Table 4      Reactivated Catalyst A.sub.4 B.sub.4 C.sub.4 D.sub.4 -1 D.sub.4 -2     D.sub.4 -3 D.sub.4 -4 D.sub.4 -5 D.sub.4 -6 D.sub.4 -7 D.sub.4 -8     D.sub.4 -9 D.sub.4 -10 D.sub.4 -11 D.sub.4 -12 D.sub.4 -13 D.sub.4 -14     D.sub.4 -15 D.sub.4 -16 D.sub.4 -17 D.sub.4      -18                            Condi- Reacti- -- -- H.sub.2 0.375N     0.375N 0.375N 0.4% 1.0% 1.0% 0.375N 0.375N 0.375N 0.1N 0.375N 0.375N     0.5% 0.3% 0.3% 0.7% 2.0% 0.3% tions vating    NaOH NaOH NaOH Hy- For-     Sodium Na.sub.2 CO.sub.3 Ba(OH).sub.2 Sr(OH).sub.2 Na.sub.2 CO.sub.3     Ba(OH).sub.2 Sr(OH).sub.2 For- Sodium Lithium Sodium Sodium Glu- of     agent       dra- malde- boro-       malde- boro- alumi- tart- for- cose     treat-        zine hyde hy-       hyde hy- num rate mate ment     dride        dride hydride for Temper- -- -- 650 30 50 100 20 60 60 100     100 100 100 80 100 20 20 20 20 20 20 reacti- ature vation (°C.)     Pressure -- -- 6.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0     1.0 1.0 1.0 1.0 1.0  (ata)  Time -- -- 12.0 3.0 6.0 3.0 3.0 3.0 3.0 3.0     3.0 3.0 3.0 3.0 1.0 3.0 3.0 3.0 3.0 3.0 3.0 Post- -- -- -- Water     washing: 100° C., -- -- -- Water washing: 100° C., 2 hrs.     Water washing: 75° C., 3 hrs. treat-    2 hrs.    Drying:     100° C., 16 hrs. Drying: 100° C., 16 hrs. ment    Drying:     100° C., 16 hrs. Elimina- Carbo- --  -- 100 10 41 56 0 0 0 54 51     50 44 49 46 0 0 0 0 0 0 tion per- naceous centage materials of poisonous     Sulfurous -- -- 29 30 80 94 72 71 90 91 89 86 77 80 79 56 70 51 49 57 52     materials materials (%) Specific surface area 43 20 19 23 29 36 23 26 26 3     6 35 35 32 32 31 23 23 26 26 25 23   (m.sup.2 /g-Ru) Amount of catalyst     91 -- -- -- 145 109 270 264 270 111 114 119 123 126 129 274 278 260 264     264 270 required for reac- tion (ml)

EXAMPLE 8

The reactivated catalysts as obtained in Example 7 (Catalysts D₄ -1 toD₄ -3, D₄ -8 and D₄ -10 to D₄ -18) were each subjected to furthertreatment for reactivation under the conditions as shown in Table 5. Thethus reactivated catalysts were each reused for continuoussteam-reforming under the same conditions as shown in Example 7. Theresults are shown in Table 5.

As seen from Table 5, the catalysts (E₅ -1 to E₅ -19) reactivated in twosteps are much more recovered in catalytic activity than the catalysts(D₄ -1 to D₄ -3, D₄ -8 and D₄ -10 to D₄ -18) reactivated in one step.

    Table 5      Catalyst E.sub.5 -1 E.sub.5 -2 E.sub.5 -3 E.sub.5 -4 E.sub.5 -5 E.sub.5     -6 E.sub.5 -7 E.sub.5 -8 E.sub.5 -9 E.sub.5 -10 E.sub.5 -11 E.sub.5 -12     E.sub.5 -13 D.sub.5 -14 E.sub.5 -15 E.sub.5 -16 E.sub.5 -17 E.sub.5 -18     D.sub.5 -19 Catalyst used D.sub.4 -1 D.sub.4 -3 D.sub.4 -8 D.sub.4 -8     D.sub.4 -10 D.sub.4 -11 D.sub.4 -12 D.sub.4 -13 D.sub.4 -13 D.sub.4 -14     D.sub.4 -1 D.sub.4 -2 D.sub.4 -10 D.sub.4 -11 D.sub.4 -12 D.sub.4 -15     D.sub.4 -16 D.sub.4 -17 D.sub.4      -18                                        Condi- Reacti- 1.0% 0.4%     0.5% 0.5% 0.5% 1.0% 0.3% 0.375N 0.1N 0.375N 0.7% 0.3% 0.3% 2.0% 0.3%     0.1N 0.1N 0.375N 0.375N tions vating Sodium Hydra- Formal- Formal-     Formal- Hydra- Sodium NaOH NaOH KOH Sodium Glu- Lithium Sodium Lithium     NaOH Na.sub.2 CO.sub.3 Ba(OH).sub.2 Sr(OH).sub.2 of agent boro- zine     dehyde dehyde dehyde zine boro-    tart- cose alumi- for- alumi- treat-     hydride      hy-    rate  num mate num ment        dride      hydride     hydride for Temper- 60 20 20 60 20 60 20 100 100 80 20 20 20 20 20 100     100 80 100 reacti- ature vation (°C.)  Pressure 1.0 1.0 1.0 1.0     1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  (ata)  Time     3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0     1.0  (hrs) Post-     treat- Water washing: 75° C., 3 hrs. Water     washing: 100° C., Water washing: 75° C., 3 hrs. Water     washing: 100° C., 2 hrs. ment Drying: 100° C., 16 hrs.     2 hrs. Drying: 100° C., 16 hrs. Drying: 100° C., 16 hrs.     Drying: 100° C., 16 hrs. Elimina- Carbo- 10 56 51 51  44 49 46 54 4     4 52 10 41 44 49 46 47 44 49 46 tion per- naceous centage materials of     poisonous Sulfurous 86 96 95 97 89 96 90 86 80 85 65 91 89 91 90 90 88     91 90 materials materials (%) Specific surface area 36 41 41 41 36 41 35 4     1 36 36 32 37 40 37 36 41 40 37 35   (m.sup.2 /g-Ru) Amount of catalyst     109 93 97 93 106 97 116 95 102 106 123 102 98 102 106 96 100 102 112     required for reac- tion (ml)

EXAMPLE 9

The reactivated catalyst obtained in Example 7 (Catalyst D₄ -13) wastreated with a 0.1 N aqueous solution of sodium hydroxide at 100° C.under 1 atm. (absolute) for 3 hours, washed with water at 100° C. for 2hours and dried at 100° C. for 16 hours. Then, the resulting catalystwas again subjected to treatment with a 0.5% aqueous solution offormaldehyde at 20° C. under 1 atm. (absolute) for 3 hours and treatmentwith a 0.1 N aqueous solution of sodium hydroxide at 100° C. under 1atm. (absolute) for 3 hours, followed by washing with water at 100° C.for 2 hours and drying at 100° C. for 16 hours. The thus reactivatedcatalyst was used for steam-reforming under the same conditions asstated in Example 7. The results are as follows: elimination percentageof poisonous materials: carbonaceous materials, 80 %, sulfurousmaterial, 100%. Specific surface area: 42 m² /g-Ru. Amount of catalystrequired for reaction: 92 ml.

As seen from the above results, the repeating treatments with a reducingsubstance and with an inorganic alkaline substance are quite effectivefor reactivation of the catalyst.

EXAMPLE 10

The reactivated catalyst obtained in Example 7 (Catalyst D₄ -17) wastreated with a 0.375 N aqueous solution of barium hydroxide at 80° C.under 1 atm. (absolute) for 3 hours, washed with water at 100° C. for 2hours and dried at 100° C. for 16 hours. Then, the resulting catalystwas again subjected to treatment with a 2.0% aqueous solution of sodiumformate at 20° C. under 1 atm. (absolute) for 3 hours and treatment witha 0.375 N aqueous solution of barium hydroxide at 80° C. under 1 atm.(absolute) for 3 hours, followed by washing with water at 100° C. for 2hours and drying at 100° C. for 16 hours. The thus reactivated catalystwas used for steam-reforming under the same conditions as stated inExample 7. The results are as follows: elimination percentage ofpoisonous materials: carbonaceous materials, 76% sulfurous material,100%. Specific surface area: 42 m² /g-Ru. Amount of catalyst requiredfor reaction: 92 ml.

As seen from the above results, the repeating treatments with aninorganic alkaline substance and with a reducing substance are quiteeffective for reactivation of the catalyst.

EXAMPLE 11

The reactivated catalysts obtained in Example 4 (Catalyst E₃ -5) and inExample 4 (Catalyst E₃ -7)) were each reused for steam-reforming underthe same conditions as shown in Example 3. The results are shown inTable 6, from which it is understood that the reactivated catalysts showthe similar behavior to the fresh catalyst (Catalyst A₂) in depressionof the catalytic activity and their catalytic activity, particularlythat of Catalyst E₃ -5, is nearly equal to the catalytic activity of thefresh catalyst.

                  Table 6                                                         ______________________________________                                        Catalyst              A.sub.2 E.sub.3 -5                                                                            E.sub.3 -7                              ______________________________________                                        Amount of catalyst                                                                          Start        92      95   102                                   required for  600 hours   164     171   183                                   reaction (ml) 1200 hours  221     232   250                                   ______________________________________                                    

EXAMPLE 12

The reactivated catalysts obtained in Example 4 (Catalyst E₃ -13) and inExample 6 were each reused for steam re-forming under the sameconditions as shown in Example 3. The results are shown in Table 7, fromwhich it is seen that the reactivated catalysts show the similarbehavior to the fresh catalyst (Catalyst A₂) in depression of thecatalytic activity and their catalytic activity, particularly that ofthe reactivated catalyst obtained in Example 6 is nearly equal to thecatalytic activity of the fresh catalyst.

                  Table 7                                                         ______________________________________                                                                           Obtained in                                Catalyst            A.sub.2                                                                              E.sub.3 -13                                                                           Example 6                                  ______________________________________                                        Amount of catalyst                                                                         Start       92    100    93                                      required for 600 hours  164    179   166                                      reaction (ml)                                                                              1200 hours 221    242   224                                      ______________________________________                                    

EXAMPLE 13

The reactivated catalysts obtained in Example 8 (Catalyst E₅ -8) and inExample 9 were each reused for steam-reforming under the same conditionsas shown in Example 7. The results are shown in Table 8, from which itis seen that the reactivated catalysts show the similar behavior to thefresh catalyst (Catalyst A₄) in depression of the catalytic activity.

                  Table 8                                                         ______________________________________                                                                           Obtained in                                Catalyst            A.sub.4                                                                              E.sub.5 -8                                                                            Example 9                                  ______________________________________                                        Amount of catalyst                                                                         Start       91     95    92                                      required for 200 hours  156    167   159                                      reaction (ml)                                                                              400 hours  222    238   226                                      ______________________________________                                    

EXAMPLE 14

The reactivated catalysts obtained in Example 8 (Catalyst E₅ -16) and inExample 10 were each reused for steam-reforming under the sameconditions as shown in Example 7. The results are shown in Table 9, fromwhich it is seen that the reactivated catalysts show the similarbehavior to the fresh catalyst (Catalyst A₄) in depression of thecatalytic activity.

                  Table 9                                                         ______________________________________                                                                           Obtained in                                Catalyst            A.sub.4                                                                              E.sub.5 -16                                                                           Example 10                                 ______________________________________                                        Amount of catalyst                                                                         Start       91     96    92                                      required for 200 hours  156    166   160                                      reaction (ml)                                                                              400 hours  222    235   229                                      ______________________________________                                    

EXAMPLE 15

A catalyst comprising 2.0% of ruthenium and 0.1% of chromium oxidedeposited on spheroidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₁₀ ") (325 ml)was charged into a tubular reactor of 1 inch in diameter, and a gaseousmixture comprising naphtha (content of sulfur, 2 ppm; final boilingpoint, 168° C.), steam, hydrogen, methane and carbon oxides was fedtherein to effect continuously steam-reforming reaction for 1500 hoursunder the following conditions:

Temperature of reactor: inlet, 450° C., outlet, 524° C.;

Space velocity: 2000 (1/hr);

Ratio of steam/hydrocarbon: 0.9 (number of oxygen atoms per one carbonatom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 1500 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₁₀ ") was treated under the conditions as shown in Table 10for reactivation. The reactivated catalyst was reused in steam-reformingreaction under the same conditions as mentioned above. The results areshown in Table 10.

As seen from Table 10, the reactivation treatment with gaseous materialsis effective for elimination of carbonaceous materials, but removal ofsulfurous materials is insufficient and the dispersibility can be hardlyrecovered so that recovery of the catalytic activity is scarcelyobserved (Catalysts C₁₀ -1 to C₁₀ -5). In the case of treatment with aninorganic alkaline substance, elimination of sulfurous materials andrecovery of the dispersibility (as well as recovery of the catalyticactivity) are good.

                                      Table 10                                    __________________________________________________________________________                       Reactivated                                                Catalyst    A.sub.10                                                                          B.sub.10                                                                         C.sub.10 -1                                                                      C.sub.10 -2                                                                        C.sub.10 -3                                                                        C.sub.10 -4                                                                       C.sub.10 -5                                                                        D.sub.10 -1                                                                       D.sub.10 -2                                                                       D.sub.10 -3                                                                         D.sub.10 -4                                                                       D.sub.10           __________________________________________________________________________                                                               -5                 Condi-                                                                             Reactivating                                                                         --  -- H.sub.2                                                                          H.sub.2 :H.sub.2 O                                                                 H.sub.2 O:N.sub.2                                                                  O.sub.2 :N.sub.2                                                                  O.sub.2 :H.sub.2 O:                                                                0.375N                                                                            0.375N                                                                             0.375N                                                                             0.375N                                                                            0.375N             tions                                                                              agent*           (=1:1                                                                              (=3:1                                                                              (=21:                                                                             N.sub.2 (=10:                                                                      NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       NaOH                                                                              NaOH               of                    by mol)                                                                            by mol)                                                                            79 by                                                                             50:40 by                                  treat-                          vol-                                                                              volume)                                   ment                            ume)                                          for  Temper-                                                                              --  -- 600                                                                              600  650  500 600  100 100  100  50  30                 reacti-                                                                            ature (°C.)                                                       vation                                                                             Pressure                                                                             --  -- 6.0                                                                              6.0  6.0  6.0 6.0  1.0 1.0  1.0  1.0 1.0                     (ata)                                                                         Time (hrs)                                                                           --  -- 6.0                                                                              6.0  12.0 5.0 10.0 1.5 3.0  3.0  6.0 10.0               Post-treat- --  -- -- --   --   --  --   Water washing: 100°                                                                  Water washing:         ment                                     2 hrs.        100° C.,                                                               hrs.                                                            Drying: 100° C., 16                                                                  Drying:                                                                       100° C., 16                                                            hrs.                   Elimina-                                                                           Carbo- --  -- 78 80   100  100 100  55  54   50   41  40                 tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            --  -- 21 28   32   40  38   95  93   87   78  75                 materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                     43  20 19 19   19   17  18   35  36   33   28  28                   (m.sup.2 /g-Ru)                                                             Amount of catalyst                                                                        52.5                                                                              -- -- --   --   --  --   63  64   66   85  --                 required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________     Note:                                                                         *In case of Catalysts C.sub.10 -1 to C.sub.10 -5, the treatment was           carried out with a space velocity of 2500 (1hr).                         

EXAMPLE 16

The reactivated catalysts as obtained in Example 15 (Catalysts C₁₀ -1,C₁₀ -2 and C₁₀ -5) were each subjected to further treatment forreactivation under the conditions as shown in Table 11. The thusreactivated catalysts were each reused for continuous steam-reformingunder the same conditions as shown in Example 15. The results are shownin Table 11.

As seen from Table 11, the catalysts (E₁₁ -1 to E₁₁ -6) reactivated intwo steps are much recovered in catalytic activity.

                                      Table 11                                    __________________________________________________________________________    Catalyst    E.sub.11 -1                                                                        E.sub.11 -2                                                                        E.sub.11 -3                                                                        E.sub.11 4                                                                         E.sub.11 5                                                                         E.sub.11 -6                                                                        E.sub.11 -7                                                                        E.sub.11 8                     Catalyst used                                                                             C.sub.10 -1                                                                        C.sub.10 -1                                                                        C.sub.10 -1                                                                        C.sub.10 -1                                                                        C.sub.10 -2                                                                        C.sub.10 -5                                                                        C.sub.10 -1                                                                        C.sub.10 -1                    __________________________________________________________________________    Condi-                                                                             Reactivating                                                                         0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.1N 0.375N                                                                             0.375N                                                                             0.375N                         tions                                                                              agent  NaOH NaOH Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       NaOH NaOH NaOH NaOH                           of                                                                            treat-                                                                        ment                                                                          for  Temper-                                                                              50   80   100  100  100  80   30   30                             reacti-                                                                            ature (°C.)                                                       vation                                                                             Pressure                                                                             1.0  1.0  1.0  1.0  1.0  1.0  1.0  1.0                                 (ata)                                                                         Time (hrs)                                                                           3.0  1.5  1.5  2.0  1.5  1.5  10.0 3.0                            Post-treat- Water washing: 100° C., 2 hrs.                             ment        Drying: 100° C., 16 hrs.                                   Elimina-                                                                           Carbo- 81   86   85   83   83   100  80   80                             tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            83   96   94   88   90   97   80   48                             materials                                                                          materials                                                                 (%)                                                                          Specific surface area                                                                     31   38   37   35   37   38   28   23                               (m.sup.2 /g-Ru)                                                             Amount of catalyst                                                                        78   58   61   63   61   58   --   --                             required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________

EXAMPLE 17

The reactivated catalysts as obtained in Example 16 (Catalysts E₁₁ -1,E₁₁ -7 and E₁₁ -7 and E₁₁ -8) were each subjected to further treatmentfor reactivation under the conditions as shown in Table 12. The thusreactivated catalysts were each reused for continuous steam-reformingunder the same conditions as shown in Example 15. The results are shownin Table 12.

As seen from Table 12, the catalysts (F₁₂ -1 to F₁₂ -11) reactivated inthree steps are much recovered in catalytic activity.

                                      Table 12                                    __________________________________________________________________________    Catalyst  F.sub.12 -1                                                                       F.sub.12 -2                                                                        F.sub.12 -3                                                                        F.sub.12 -4                                                                         F.sub.12 -5                                                                       F.sub.12 -6                                                                       F.sub.12 -7                                                                        F.sub.12 -8                                                                        F.sub.12                                                                           F.sub.12 -10                                                                       F.sub.12 -11        Catalyst used                                                                           E.sub.11 -1                                                                       E.sub.11 -1                                                                        E.sub.11 -1                                                                        E.sub.11 -1                                                                         E.sub.11 -1                                                                       E.sub.11 -7                                                                       E.sub.11 -7                                                                        E.sub.11 -7                                                                        E.sub.11 -7                                                                        E.sub.11 -7                                                                        E.sub.11            __________________________________________________________________________                                                              -8                  Condi-                                                                             Reacti-                                                                            0.4%                                                                              0.5% 0.3% 0.3%  0.3%                                                                              0.4%                                                                              0.5% 0.3% 0.7% 2.0% 1.0%                tions                                                                              vating                                                                             Hydra-                                                                            Formal-                                                                            Sodium                                                                             Lithium                                                                             Glu-                                                                              Hydra-                                                                            Formal-                                                                            Sodium                                                                             Sodium                                                                             Sodium                                                                             Hydra-              of   agent                                                                              zine                                                                              dehyde                                                                             boro-                                                                              aluminum                                                                            cose                                                                              zine                                                                              dehyde                                                                             boro-                                                                              tart-                                                                              formate                                                                            zine                treat-             hydride                                                                            hydride            hydride                                                                            rate                          ment                                                                          for  Temper-                                                                            20  20   20   20    20  20  20   20   20   20   60                  reacti-                                                                            ature                                                                    vation                                                                             (° C.)                                                                 Pressure                                                                           1.0 1.0  1.0  1.0   1.0 1.0 1.0  1.0  1.0  1.0  1.0                      (ata)                                                                         Time 3.0 3.0  3.0  3.0   3.0 3.0 3.0  3.0  3.0  3.0  3.0                      (hrs)                                                                    Post-                                                                         treat-    Water washing: 75° C., 3 hrs.                                ment      Drying: 100° C., 16 hrs.                                     Elimina-                                                                           Carbo-                                                                             81  81   81   81    81  80  80   80   80   80   80                  tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                          96  90   95   92    92  92  87   90   91   93   94                  materials                                                                          materials                                                                 (%)                                                                          Specific surface area                                                                   41  40   40   40    40  37  36   35   36   36   39                    (m.sup.2 /g-Ru)                                                             Amount of catalyst                                                                      53  55   56   53    56  60  61   63   61   61   56                  required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________

EXAMPLE 18

The reactivated catalysts obtained in Example 16 (Catalyst E₁₁ -2) andin Example 17 (Catalyst F₁₂ -1) were each reused for steam-reformingunder the same conditions as shown in Example 15. The results are shownin Table 13, from which it is seen that the reactivated catalysts showthe similar behavior to the fresh catalyst (Catalyst A₁₀) in depressionof the catalytic activity and their catalytic activity, particularlythat of Catalyst F₁₂ -1 is nearly equal to the catalytic activity of thefresh catalyst.

                  Table 13                                                        ______________________________________                                        Catalyst           A.sub.10 E.sub.11 -2                                                                            F.sub.12 -1                              ______________________________________                                        Amount of catalyst                                                                         Start     52.5     58     53                                     required for 300 hours 123.5    139.5  125                                    reaction (ml)                                                                              600 hours 183      208.5  186                                                 900 hours 252      289    257                                    ______________________________________                                    

EXAMPLE 19

A catalyst comprising 2.6% of ruthenium and 0.1% of chromium oxidedeposited on spheroidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₁₄ ") (325 ml)was charged into a tubular reactor of 1 inchin diameter, and a gaseousmixture comprising naphtha (content of sulfur, 2 ppm; final boilingpoint, 168° C.), steam, hydrogen, methane and carbon oxides was fedtherein to effect continuously steam-reforming reaction for 2400 hoursunder the following conditions:

Temperature of reaction: inlet, 400° C., outlet 517° C;

Space velocity: 1500 (1/hr);

Ratio of steam/hydrocarbon: 0.7 (number of oxygen atoms per one carbonatom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 2400 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₁₄ ") was treated under the conditions as shown in Table 14for reactivation. The reactivated catalyst was reused in steam-reformingreaction under the same conditions as mentioned above. The results areshown in Table 14.

As seen from Table 14, the reactivation treatment with gaseous materialsis effective for elimination of carbonaceous materials, but removal ofsulfurous materials is insufficient and the dispersibility can be hardlyrecovered so that recovery of the catalytic activity is scarcelyobserved (Catalysts C₁₄ -1 to C₁₄ -5). In the case of treatment with aninorganic alkaline substance, elimination of sulfurous materials andrecovery of the dispersibility (as well as recovery of the catalyticactivity) are good.

    Table 14      Reactivated Catalyst A.sub.14 B.sub.14 C.sub.14 -1 C.sub.14 -2 C.sub.14     -3 C.sub.14 -4 C.sub.14 -5 D.sub.14 -1 D.sub.14 -2 D.sub.14 -3 D.sub.14     -4 D.sub.14 -5 D.sub.14 -6 D.sub.14 -7 D.sub.14 -8 D.sub.14      -9             Condi- Reactivating -- -- H.sub.2 H.sub.2 :H.sub.2 O     H.sub.2 O:N.sub.2 O.sub.2 :N.sub.2 O.sub.2 :H.sub.2 O 0.375N 0.375N     0.375N 0.375N 0.375N 0.375N 0.1N 0.375N 0.375N tions agent*    (=1:1     (=3:1 (=21: N.sub.2 (=10: NaOH NaOH NaOH NaOH Na.sub.2      CO.sub.3 Ba(OH).sub.2 NaOH Na.sub.2 CO.sub.3 Ba(OH).sub.2 of     by     mol) by mol) 79 by 50:40 by treat-       volume) volume) ment for     Temper- -- -- 600 600 650 500 600 30 30 50 100 100 100 100 80 100     reacti- ature (°C.) vation  Pressure -- -- 6.0 6.0 6.0 6.0 6.0     1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  (ata)  Time (hrs) -- -- 6.0 6.0     12.0 5.0 10.0 3.0 10.0 6.0 3.0 3.0 3.0 3.0 3.0 1.5 Post-treat- -- -- --     -- -- -- -- Water washing: 100° C., Water washing: 100°     C., 2 hrs. ment        2 hrs. Drying: 100° C., 16 hrs.     Drying: 100° C., 16 hrs. Elimina- Carbo- -- -- 75 78 100  100     100  12 41 43 52 51 47 40 44 45 tion per- naceous centage materials of     poisonous Sulfurous -- -- 19 25 30 37 35 32 72 78 90 88 82 75 77 76     materials materials (%) Specific surface area 43 20 19 19  19 17 18 21     27 28 34 34 32 30 30 29 (m.sup.2 /g-Ru) Amount of catalyst 92 -- -- --     -- -- -- -- -- 147  110  112  116  120  122  127  required for reac-     tion (ml)     Note:     *In case of Catalysts C.sub.14 -1 to C.sub.14 -5, the treatment was     carried out with a space velocity of 2500.sup.14 (1/hr).

EXAMPLE 20

The reactivated catalysts as obtained in Example 19 (Catalysts D₁₄ -7 toD₁₄ -9) were each subjected to further treatment for reactivation underthe conditions as shown in Table 15. The thus reactivated catalysts wereeach reused for continuous steam-reforming under the same conditions asshown in Example 19. The results are shown in Table 15.

As seen from Table 15, the catalysts (E₁₅ -1 to E₁₅ -5) reactivated intwo steps are much recovered in catalytic activity.

                                      Table 15                                    __________________________________________________________________________    Catalyst    E.sub.15 -1                                                                        E.sub.15 -2                                                                        E.sub.15 -3                                                                         E.sub.15 -4                                                                        E.sub.15 -5                                  Catalyst used                                                                             D.sub.14 -7                                                                        D.sub.14 -7                                                                        D.sub.14 -7                                                                         D.sub.14 -8                                                                        D.sub.14 -9                                  __________________________________________________________________________    Condi-                                                                             Reactivating                                                                         H.sub.2                                                                            H.sub.2 :H.sub.2 O                                                                 0.sub.2 :H.sub.2 O                                                                  H.sub.2                                                                            H.sub.2 :H.sub.2 O                           tions                                                                              agent*                                                                   of               ( = 1:1                                                                            N.sub.2 ( = 10:                                                                          ( = 1:1                                      treat-           by mol)                                                                            50:40 by   by mol)                                      ment                  volume)                                                 for  Temper-                                                                              600  600  600   650  650                                          reacti-                                                                            ature (°C.) -vation                                                    Pressure                                                                             6.0  6.0  6.0   6.0  6.0                                               (ata)                                                                         Time (hrs)                                                                           6.0  6.0  10.0  12.0 12.0                                              Post-treat-                                                                          --   --   --    --   --                                                ment                                                                     Elimina-                                                                           Carbo- 85   87   100   100  100                                          tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            80   81   84    81   82                                           materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                     31   31   30    30   30                                           (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                        105  105  110   110  112                                          required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________     Note:                                                                         *In case of Catalysts E.sub.15 -1 to E.sub.15 -5, the treatment was           carried out with a space velocity of 2500 (1/hr).                        

EXAMPLE 21

The reactivated catalysts as obtained in Example 19 (Catalysts D₁₄ -1 toD₁₄ -4, D₁₄ -8 and D₁₄ -9) were each subjected to further treatment forreactivation under the conditions as shown in Table 16. The thusreactivated catalysts were each reused for continuous steam-reformingunder the same conditions as shown in Example 19. The results are shownin Table 16.

As seen from Table 16, the catalysts (E₁₆ -1 to E₁₆ -10) reactivated intwo steps are much recovered in catalytic activity.

                                      Table 16                                    __________________________________________________________________________    Catalyst     E.sub.16 -1                                                                        E.sub.16 -2                                                                        E.sub.16 -3                                                                        E.sub.16 -4                                                                        E.sub.16 -5                                                                        E.sub.16 -6                                                                        E.sub.16 -7                                                                        E.sub.16 -8                                                                        E.sub.16 -9                                                                        E.sub.16 -10        Catalyst used                                                                              D.sub.14 -1                                                                        D.sub.14 -2                                                                        D.sub.14 -3                                                                        D.sub.14 -3                                                                        D.sub.14 -3                                                                        D.sub.14 -4                                                                        D.sub.14 -8                                                                        D.sub.14 -8                                                                        D.sub.14 -9                                                                        D.sub.14            __________________________________________________________________________                                                              -9                  Condi-                                                                              Reactivating                                                                         1.0% 0.4% 0.3% 0.5% 0.3% 0.3% 0.5% 0.7% 0.4% 2.0%                tions agent  Hydra-                                                                             Hydra-                                                                             Lithium                                                                            Formal-                                                                            Sodium                                                                             Glucose                                                                            Formal-                                                                            Sodium                                                                             Hydra-                                                                             Sodium              of           zine zine alumi-                                                                             dehyde                                                                             boro-     dehyde                                                                             tart-                                                                              zine formate             treat-                 num       hydride        rate                          ment                   hydride                                                for   Temper-                                                                              60   20   20   20   20   20   20   20   20   20                  reacti-                                                                             ature (°C.)                                                      vation                                                                              Pressure                                                                             1.0  1.0  1.0  1.0  1.0  1.0  1.0  1.0  1.0  1.0                       (ata)                                                                         Time (hrs)                                                                           3.0  3.0  3.0  3.0  3.0  3.0  3.0  3.0  3.0  3.0                 Post-treat-  Water washing: 75° C., 3 hrs.                             ment         Drying: 100° C., 16 hrs.                                  Elimina-                                                                            Carbo- 12   41   43   43   43   52   44   44   45   45                  tion per-                                                                           naceous                                                                 centage                                                                             materials                                                               of                                                                            poisonous                                                                           Sulfurous                                                                            89   91   93   93   93   97   90   88   92   90                  materials                                                                           materials                                                               (%)                                                                           Specific surface area                                                                      34   36   36   36   34   40   36   36   36   36                  (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                         108  110  102  106  108  95   106  106  102  102                 required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________

EXAMPLE 22

The reactivated catalysts as obtained in Example 21 (Catalysts E₁₆ -1,E₁₆ -3 and E₁₆ -5 to E₁₆ -7) were each subjected to further treatmentfor reactivation under the conditions as shown in Table 17. The thusreactivated catalysts were each reused for continuous steam-reformingunder the same conditions as shown in Example 15. The results are shownin Table 17.

As seen from Table 17, the catalysts (F₁₇ -1 to F₁₇ -5) reactivated inthree steps are much recovered in catalytic activity.

                                      Table 17                                    __________________________________________________________________________    Catalyst    F.sub.17 -1                                                                       F.sub.17 -2                                                                       F.sub.17 -3                                                                        F.sub.17 -4                                                                        F.sub.17 -5                                     Catalyst used                                                                             E.sub.16 -1                                                                       E.sub.16 -3                                                                       E.sub.16 -5                                                                        E.sub.16 -6                                                                        E.sub.16 -7                                     __________________________________________________________________________    Condi-                                                                             Reactivating                                                                         H.sub.2                                                                           H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 H.sub.2 O:N.sub.2                                                                  O.sub.2 :H.sub.2 O:N.sub.2                      tions                                                                              agent*         (=1:1                                                                              (=3:1                                                                              (=10:50:40                                      of                  by mol)                                                                            by mol)                                                                            by volume)                                      treat-                                                                        ment                                                                          for  Temper-                                                                              650 600 600  650  600                                             reacti-                                                                            ature (° C.)                                                      vation                                                                             Pressure                                                                             6.0 6.0 6.0  6.0  6.0                                                  (ata)                                                                         Time (hrs)                                                                           12.0                                                                              6.0 6.0  12.0 10.0                                                 Post-treat-                                                                          --  --  --   --   --                                                   ment                                                                     Elimina-                                                                           Carbo- 100 86  87   100  100                                             tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            96  96  96   97   94                                              materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                     35  37  35   40   37                                              (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                        100 96  102  93   98                                              required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________     Note:                                                                         *In case of Catalysts F.sub.17 -1 to F.sub.17 -5, the treatment was           carried out with a space velocity of 2500 (1/hr).                        

EXAMPLE 23

The reactivated catalysts obtained in Example 20 (Catalyst E₁₅ -1) andin Example 22 (Catalyst F₁₇ -4) were each reused for steam-reformingunder the same conditions as shown in Example 19. The results are shownin Table 18, from which it is seen that the reactivated catalysts showthe similar behavior to the fresh catalyst (Catalyst A₁₄) in depressionof the catalytic activity and their catalytic activity, particularlythat of Catalyst F₁₇ -4, is nearly equal to the catalytic activity ofthe fresh catalyst.

                  Table 18                                                        ______________________________________                                        Catalyst            A.sub.14                                                                              E.sub.15 -1                                                                            F.sub.17 -4                              ______________________________________                                        Amount of catalyst                                                                         Start       92     105     93                                    required for 600 hours  164     191    168                                    reaction (ml)                                                                              1200 hours 221     260    227                                    ______________________________________                                    

EXAMPLE 24

A catalyst comprising 2% of ruthenium deposited on spheroidal particlesof alumina of 4 mm in diameter (hereinafter referred to as "Catalyst A₁₈") (6700 ml) was charged into a tubular reactor of 5 inch in diameter,and methanol and steam were fed therein to effect continuouslysteam-reforming reaction for 2000 hours under the following conditions:

Temperature of reactor: inlet, 580° C., outlet, 620° C.;

Space velocity: 15800 (1/hr);

Ratio of steam/methanol: 1.5 (by mol);

Pressure: 6 atm. (absolute)

After 2000 hours, the catalyst (hereinafter referred to as "Catalyst B₁₈") was treated under the same conditions as shown in Table 18 forreactivation. The reactivated catalyst was reused in steam-reformingreaction under the same conditions as mentioned above. The results areshown in Table 18.

As seen from Table 18, treatment with an inorganic alkaline substance ora reducing substance shows recovery of the catalytic activity.

                                      Table 18                                    __________________________________________________________________________                       Reactivated                                                Catalyst     A.sub.18                                                                         B.sub.18                                                                         D.sub.18 -1                                                                         D.sub.18 -2                                                                         D.sub.18 -3                                                                         D.sub.18 -4                              __________________________________________________________________________    Condi-                                                                              Reactivating                                                                         -- -- 0.375N                                                                              0.375N                                                                              1.0%  0.3%                                     tions agent        NaOH  NaOH  Hydra-                                                                              Glucose                                  of                             zine                                           treat-                                                                        ment                                                                          for   Temper-                                                                              -- -- 30    100   60    20                                       reacti-                                                                             ature (°C.)                                                      vation                                                                              Pressure                                                                             -- -- 1.0   1.0   1.0   1.0                                            (ata)                                                                         Time (hrs)                                                                           -- -- 3.0   3.0   3.0   3.0                                      Post-treat-  -- -- Water washing:                                                                            Water washing:                                 ment               100° C., 2 hrs.                                                                    75° C., 3 hrs.                                             Drying: 100° C., 16 hrs.                                                           Drying: 100° C., 16 hrs.                Elimina-                                                                            Carbo- -- -- 12    53     0     0                                       tion per-                                                                           naceous                                                                 centage                                                                             materials                                                               of                                                                            poisonous                                                                           Sulfurous                                                                            -- -- --    --    --    --                                       materials                                                                           materials                                                               (%)                                                                           Specific surface area                                                                      43 17 20    34    23    23                                       (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                         1.3                                                                              -- --    1.6   3.8   4.0                                      required for reac-                                                            tion (1)                                                                      __________________________________________________________________________

EXAMPLE 25

The reactivated catalysts as obtained in Example 24 (Catalysts D₁₈ -1 toD₁₈ -4) were each subjected to further treatment for reactivation underthe conditions as shown in Table 19. The thus reactivated catalysts wereeach reused for continuous steam-reforming under the same conditions asshown in Example 24. The results are shown in Table 19.

As seen from Table 19, the catalysts (E₁₉ -1 to E₁₉ -4) reactivated intwo steps are much more recovered in catalytic activity than thecatalysts (D₁₈ -1 to D₁₈ -4) reactivated in one step.

                  Table 19                                                        ______________________________________                                        Catalyst       E.sub.19 -1                                                                           E.sub.19 -2                                                                            E.sub.19 -3                                                                         E.sub.19 -4                             Catalyst used  D.sub.18 -1                                                                           D.sub.18 -2                                                                            D.sub.18 -3                                                                         D.sub.18 -4                             ______________________________________                                        Condi-  Reactivating                                                                             1.0%    0.3%   0.375N                                                                              0.375N                                tions   agent      Hydra-  Sodium NaOH  NaOH                                  of                 zine    boro-                                              treat-                     hydride                                            ment                                                                          for     Temperature                                                                              60      20     100   80                                    reacti- (°C.)                                                          vation                                                                                Pressure   1.0     1.0    1.0   1.0                                           (ata)                                                                         Time (hrs) 3.0     3.0    3.0   3.0                                   Post-treat-    Water washing:                                                                             Water washing:                                    ment           75° C., 3 hrs.                                                                      100° C., 2 hrs.                                           Drying:      Drying:                                                          100° C., 16 hrs.                                                                    100° C., 16 hrs.                           Elimina-                                                                              Carbo-     12      52     52    50                                    tion per-                                                                             naceous                                                               centage materials                                                             of                                                                            poisonous                                                                             Sulfurous  --      --     --    --                                    materials                                                                             materials                                                             (%)                                                                           Specific surface area                                                                        34      40       41    38                                      (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                           1.5     1.4      1.3   1.4                                     required for reac-                                                            tion (1)                                                                      ______________________________________                                    

EXAMPLE 26

A catalyst comprising 2.0% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter as a carrier material(hereinafter referred to as "Catalyst A₂₀ ") (290 ml) was charged into atubular reactor of 1 inch in diameter, and methane (content of sulfur, 2ppm) and air were fed therein to effect continuously partial oxidationfor 2500 hours under the following conditions:

Temperature of reactor: inlet, 310° C., outlet, 700° C.;

Space velocity: 17500 (1/hr);

Ratio of air/methane: 2.37 (by mol);

Pressure: 1 atm. (absolute)

After 2500 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₂₀ ") was treated under the conditions as shown in Table 20for reactivation. The reactivated catalyst was reused in partialoxidation under the same conditions as mentioned above. The results areshown in Table 20.

As seen from Table 20, treatment with an inorganic alkaline substance ora reducing substance shows recovery of the catalytic activity.

                                      Table 20                                    __________________________________________________________________________                       Reactivated                                                Catalyst     A.sub.20                                                                         B.sub.20                                                                         D.sub.20 -1                                                                         D.sub.20 -2                                                                         D.sub.20 -3                                                                         D.sub.20 -4                              __________________________________________________________________________    Condi-                                                                              Reactivating                                                                         -- -- 0.375N                                                                              0.375N                                                                              1.0%  2.0%                                     tions agent        NaOH  NaOH  Formal-                                                                             Sodium                                   of                             dehyde                                                                              formate                                  treat-                                                                        ment                                                                          for   Temper-                                                                              -- -- 30    100   60    20                                       reacti-                                                                             ature (°C.)                                                      vation                                                                              Pressure                                                                             -- -- 1.0   1.0   1.0   1.0                                            (ata)                                                                         Time (hrs)                                                                           -- -- 3.0   3.0   3.0   3.0                                      Post-treat-  -- -- Water washing: 100° C.,                                                            Water washing: 75°  C.,                 ment               2 hrs.      3 hrs.                                                            Drying: 100° C., 16 hrs.                                                           Drying: 100° C., 16 hrs.                Elimina-                                                                            Carbo- -- -- 12    52    0     0                                        tion per-                                                                           naceous                                                                 centage                                                                             materials                                                               of                                                                            poisonous                                                                           Sulfurous                                                                            -- -- 32    95    70    55                                       materials                                                                           materials                                                               (%)                                                                           Specific surface area                                                                      43 17 21    33    21    21                                       (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                         58 -- --    67    170   172                                      required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________

EXAMPLE 27

The reactivated catalysts as obtained in Example 26 (Catalysts D₂₀ -1 toD₂₀ -4) were each subjected to further treatment for reactivation underthe conditions as shown in Table 21. The thus reactivated catalysts wereeach reused for continuous partial oxidation under the same conditionsas shown in Example 26. The results are shown in Table 21.

As seen from Table 21, the catalysts (E₂₁ -1 to E₂₁ -4) reactivated intwo steps are much more recovered in catalytic activity than thecatalysts (D₂₀ -1 to D₂₀ -4) reactivated in one step.

                                      Table 21                                    __________________________________________________________________________    Catalyst    E.sub.21 -1                                                                           E.sub.21 -2                                                                        E.sub.21 -3                                                                           E.sub.21 -4                                  Catalyst used                                                                             D.sub.20 -1                                                                           D.sub.20 -1                                                                        D.sub.20 -3                                                                           D.sub.20 -4                                  __________________________________________________________________________    Condi-                                                                             Reactivating                                                                         1.0%    0.3% 0.375N  0.375N                                       tions                                                                              agent  Hydra-  Sodium                                                                             NaOH    NaOH                                         of          zine    boro-                                                     treat-              hydride                                                   ment                                                                          for  Temper-                                                                              60      20   80      80                                           reacti-                                                                            ature (°C.)                                                       vation                                                                             Pressure                                                                             1.0     1.0  1.0     1.0                                               (ata)                                                                         Time (hrs)                                                                           3.0     3.0  3.0     3.0                                               Post-treat-                                                                          Water washing:                                                                        75° C.,                                                                     Water washing:                                                                        100° C.,                                   ment           3 hrs.       2 hrs.                                                   Drying: 100° C.,                                                               16 hrs.                                                                            Drying: 100° C.,                                                               16 hrs.                                      Elimina-                                                                           Carbo- 12      52   47      47                                           tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            95      97   92      93                                           materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                     34      40   39      37                                           (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                        68      62   60      62                                           required for reac-                                                            tion (ml)                                                                     __________________________________________________________________________

EXAMPLE 28

A catalyst comprising 1.0% of ruthenium and 0.1% of chromium oxidedeposited on spheoidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₂₃ ") (400 ml)was charged into a tubular reactor of 1 inch in diameter, and a gaseousmixture comprising naphtha (content of sulfur, 2 ppm; final boilingpoint, 108° C.) and hydrogen was fed therein to effect continuouslyhydro-cracking for 700 hours under the conditions as shown in Table 22:

                  Table 22                                                        ______________________________________                                        Temperature of      265° C.                                            reactor at inlet                                                              Pressure            46 atm. (absolute)                                        Ratio of hydrogen/  1.20 (by mol)                                             hydrocarbon                                                                   Mass velocity       500 kg-mol/m.sup.2.hr                                     ______________________________________                                    

After 700 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₂₃ ") was treated under the conditions as shown in Table 23for reactivation. The reactivated catalyst was reused in hydro-crackingunder the same conditions as mentioned above. The results are shown inTable 23.

As seen from Table 23, the reactivation treatment with hydrogen isextremely effective for elimination of carbonaceous materials, butremoval of sulfurous materials is insufficient and the dispersibilitycan be hardly recovered so that recovery of the catalytic activity isscarcely observed (Catalyst C₂₃). In the case of treatment with aninorganic alkaline substance at room temperature for a long time,elimination of sulfurous materials and recovery of the dispersibilityare good, but recovery of the catalytic activity is still not good(Catalysts D₂₃ -1 and D₂₃ -2). When treated with an inorganic alkalinesubstance under heating, recovery of the catalytic activity is good(Catalysts D₂₃ -3, D₂₃ -4, D₂₃ -5, D₂₃ -14, D₂₃ -15, D₂₃ -16). On theother hand, sole treatment with an aqueous solution of hydrazine iseffective in removal of sulfurous materials but almost ineffective inremoval of carbonaceous materials. Nevertheless, a tendency to recoveryof the catalytic activity is seen (Catalysts D₂₃ -6 to D₂₃ -13).

    Table 23      Reactivated Catalyst A.sub.23 B.sub.23 C.sub.23 D.sub.23 -1 D.sub.23 -2 D     .sub.23 -3 D.sub.23 -4 D.sub.23 -5 D.sub.23 -6 D.sub.23 -7 D.sub.23 -8     D.sub.23 -9 D.sub.23 -10 D.sub.23 -11 D.sub.23 -12 D.sub.23 -13 D.sub.23     -14 D.sub.23      -15 D.sub.23 -16                                                        0     .4% 0.3% 0.7% 2.0% 0.3% 1.0% 1.0% 1.0%    Condi- Reactivating -- --     H.sub.2 0.375N 0.375N O.375N 0.375N 0.375N Hydra- Lithium Sodium Sodium     Glu- Hydra- Form Sodium 5.0N 0.375N 0.375N tions agent*    NaOH NaOH     NaOH NaOH NaOH zine alumi- tart- for- cose zine alde- borohy- NaOH     Na.sub.2 CO.sub.3 Ba(OH).sub.2 treat-           num hy- rate mate   hyde     dride ment           dride for Temperature -- -- 650 30 30 50 100 148 20     20 20 20 20 60 60 60 100 100 100 reacti- (°C.) vation  Pressure     -- -- 6.0 1.0 1.0 1.0 1.0 5.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0     1.0  (ata)  Time (hrs) -- -- 12.0 3.0 10.0 6.0 3.0 1.0 3.0 3.0 3.03.0     3.0 3.0 3.0 3.0 3.0 3.0 3.0 Post-treat-    Water washing: 100°     C., 2 hrs. Water washing: 75°      C., 3 hrs. Water washing: 75°  C., 3 hrs. Water washing:     100° C., ment -- -- --    2 hrs.     Drying: 100° C., 16     hrs. Drying: 100° C., 16 hrs. Drying: 100° C., 16 hrs.     Drying: 100° C., 16 hrs. Elimina- Carbo-                    tion     per- naceous -- -- 100 10 30 35 47 50 0 0 0 0 0 0 0 0 50 43 40 centage     materials of poisonous Sulfurous materials materials -- -- 20 40 73 79     90 100 70 51 51 54 51 91 69 88 95 86 82 (%) Specific surface area                 (m.sup.2 /g-Ru) 43 25 25 27 28 31 36 36 28 29 29 29 29 29 29     29 38 36 32 Conversion of hydrogen 88 5 5 7 8 50 68 69 40 39 39 39 38 45     39 38 70 68 65 (%)

EXAMPLE 29

The reactivated catalysts as obtained in Example 28 (Catalysts D₂₃ -1 toD₂₃ -12) were each subjected to further treatment for reactivation underthe conditions as shown in Table 24. The thus reactivated catalysts wereeach reused for continuous hydro-cracking under the same conditions asshown in Example 28. The results are shown in Table 24.

As seen from Table 24, the catalyst (E₂₄ -1 to E₂₄ -20) reactivated intwo steps are much more recovered in catalytic activity than thecatalysts (D₂₃ -1 to D₂₃ -12) reactivated in one step.

    Table 24      Catalyst E.sub.24 -1 E.sub.24 -2 E.sub.24 -3 E.sub.24 -4 E.sub.24 -5     E.sub.24 -6 E.sub.24 -7 E.sub.24 -8 E.sub.24 -9 E.sub.24 -10 E.sub.24     -11 E.sub.24 -12 E.sub.24 -13 E.sub.24 -14 E.sub.24 -15 E.sub.24 -16     E.sub.24 -17 E.sub.24 -18 E.sub.24 -19 E.sub.24 -20 Catalyst used     D.sub.23 -1 D.sub.23 -2 D.sub.23 -3 D.sub.23 -3 D.sub.23 -4 D.sub.23 -4     D.sub.23 -6 D.sub.23 -6 D.sub.23 -11 D.sub.23 -12 D.sub.23 -1 D.sub.23     -2 D.sub.23 -3 D.sub.23 -3 D.sub.23 -4 D.sub.23 -4 D.sub.23 -7 D.sub.23     -8 D.sub.23 -9 D.sub.23      -10                                                Condi- Reactivating     1.0% 0.4% 0.4% 0.5% 0.4% 0.3% 0.375N 0.375N 0.375N 0.375N 0.3% 0.3% 0.7% 2     .0% 0.3% 0.3% 0.375N 0.1N 0.375N 0.375 tions agent Hydra- Hydra- Hydra-     Form- Hydra- Sodium NaOH NaOH NaOH NaOH Lithium Lithium Sodium Sodium     Lithium Glu- NaOH NaOH NaOH NaOH of  zine zine zine alde- zine boro-     alum- alum- tart- for- alum- cose treat-     hyde  hy-     inum inum     rate mate inum ment       dride     hydride hydride   hydride for     Temperature 60 20 20 20 20 20 50 100  100  100  20 20 20 20 20 20 50 100      100  80 reacti- (°C.) vation Pressure 1.0 1.0 1.0 1.0 1.0 1.0     1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  (ata)  Time     (hrs) 3.0 3.0 3.0 3.0 3.0 3.0 6.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0     6.0 3.0 1.5 3.0 Post-treat- Water washing: 75° C., 3 hrs. Water     washing: 100° C., 2 hrs. Water washing: 75° C., 3 hrs.     Water washing: 100° C., 2 hrs. ment Drying: 100° C., 16     hrs. Drying: 100° C., 16 hrs. Drying: 100° C., 16 hrs.     Drying: 100° C., 16 hrs. Elimina- Carbo- 10 30 35 35 47 47 35 49     48 39 10 30 35 35 47 47 35 36 38 39 tion per- naceous centage materials     of poisonous Sulfurous 91 93 95 95 98 97 93 98 97 91 68 88 91 92 97 97     91 90 95 94 materials materials (%) Specific surface area 36 38 38 38 40 4     0 37 40 42 40 36 38 39 39 42 41 39 39 39 39 (m.sup.2 /g-Ru) Conversion     of hydrogen 48 51 74 70 80 77 74 80 81 80 50 50 74 74 81 80 77 74 74 74     (%)

EXAMPLE 30

The reactivated catalyst obtained in Example 28 (Catalyst D₂₃ -3) wastreated with a 0.4% aqueous solution of hydrazine at 20° C. under 1 atm.(absolute) for 3 hours, washed with water at 75° C. for 3 hours anddried at 100° C. for 16 hours. Then, the resulting catalyst was againsubjected to treatment with a 0.375 N aqueous solution of sodiumhydroxide at 50° C. under 1 atm. (absolute) for 6 hours and treatmentwith a 0.4% aqueous solution of hydrazine at 20° C. under 1 atm.(absolute) for 3 hours, followed by washing with water at 75° C. for 3hours and drying at 100° C. for 16 hours. The thus reactivated catalystwas used for hydro-cracking under the same conditions as shown in Table22. The results are shown in Table 25.

                  Table 25                                                        ______________________________________                                        Catalyst                     F                                                Elimination per-                                                                              Carbon-                                                       centage of      aceous       70                                               poisonous       materials                                                     materials                                                                     (%)             Sulfurous                                                                     materials    100                                              Specific surface area    42                                                   (m.sup.2 /g-Ru)                                                               Conversion of hydrogen (%)                                                                             81                                                   ______________________________________                                    

As seen from the above results, the repeating treatments with aninorganic alkaline substance and with a reducing substance are quiteeffective for reactivation of the catalyst.

EXAMPLE 31

The reactivated catalysts obtained in Example 29 (Catalysts E₂₄ -5 andE₂₄ -7) were used for continuous hydro-cracking under the conditions asshown in Example 28. The reactivated catalysts showed a similar tendencyto a freshly prepared catalyst (Catalyst A₂₃) in depression of thecatalytic activity.

EXAMPLE 32

A catalyst comprising 0.3% of ruthenium and 0.1% of chromium oxidedeposited on spheroidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₂₈ ") (1000 ml)was charged into a tubular reactor of 1 inch in diameter, and naphtha(content of sulfur, 2 ppm; final boiling point, 108° C.) and hydrogenwere fed therein to effect continously hydro-cracking reaction under theconditions as shown in Table 27.

                  Table 27                                                        ______________________________________                                        Temperature of    265°  C.                                             reactor at inlet                                                              Pressure          46 atm. (absolute)                                          Ratio of hydrogen/                                                                              1.20 (by mol)                                               hydrocarbon                                                                   Mass velocity     500 kg-mol/m.sup.2 . hr                                     ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₂₈ ") was treated under the conditions as shown in Table 28for reactivation. The reactivated catalyst was reused in hydro-crackingreaction under the same conditions as mentioned above. The results areshown in Table 28.

As seen from Table 28, the reactivation treatment with gaseous materialssuch as hydrogen, hydrogen-steam, oxygen-nitrogen andoxygen-nitrogen-steam is extremely effective for elimination ofcarbonaceous materials, but removal of sulfurous materials is notachieved and the dispersibility can be hardly recovered so that recoveryof the catalytic activity is not observed (Catalysts C₂₈ -1 to C₂₈ -5).In the case of treatment with an inorganic alkaline substance at roomtemperature, elimination of sulfurous materials is accomplished, but nocatalytic activity is recognized (Catalyst D₂₈ -5). When treated with aninorganic alkaline substance under heating, elimination of sulfurousmaterials and recovery of the dispersibility as well as recovery of thecatalytic activity are good (Catalysts D₂₈ -1 to D₂₈ -4).

                                      Table 28                                    __________________________________________________________________________                     Reactivated                                                  Catalyst   A.sub.28                                                                         B.sub.28                                                                         C.sub.28 -1                                                                       C.sub.28 -2                                                                        C.sub.28 -3                                                                        C.sub.28 -4                                                                        C.sub.28 -5                                                                        D.sub.28 -1                                                                       D.sub.28 -2                                                                        D.sub.28 -3                                                                        D.sub.28 -4                                                                       D.sub.28           __________________________________________________________________________                                                               -5                 Condi-                                                                             Reactivat-                                                                          -- -- H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 H.sub.2 O:N.sub.2                                                                  O.sub.2 :N.sub.2                                                                   O.sub.2 :H.sub.2 O:                                                                0.375N                                                                            0.375N                                                                             o.375N                                                                             0.375N                                                                            0.375N             tions                                                                              ing agent*)     (1:1 (3:1 (21:79                                                                             N.sub.2 (10:50                                                                     NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       NaOH                                                                              NaOH               of                   by mol)                                                                            by mol)                                                                            by   :40 by                                    treat-                         volume)                                                                            volume)                                   ment Tempera-                                                                            -- -- 600 600  650  500  600  100 100  100  50  30                 for  ture (°C.)                                                        reacti-                                                                            Pressure                                                                            -- -- 6.0 6.0  6.0  6.0  6.0  1.0 1.0  1.0  1.0 1.0                vation                                                                             (ata)                                                                         Time (hrs)                                                                          -- -- 6.0 6.0  12.0 5.0  10.0 1.5 3.0  3.0  6.0 10.0               Post-treat-                                                                              -- -- --  --   --   --   --   Water washing: 100° C., 2                                              hrs.                                 ment                                     Drying: 100° C., 16 hrs.      Elimina-                                                                           Carbo-                                                                   tion per-                                                                          naceous                                                                             -- -- 76  78   100  100  100  44  43   40   35  30                 centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                materials                                                                          materials                                                                           -- -- 28  31   34   42   40   88  86   82   79  73                 (%)                                                                           Specific surface area                                                         (m.sup.2 /g-Ru)                                                                          43 25 25  25   25   23   24   34  36   32   31  28                 Conversion of                                                                 hydrogen (%)                                                                             89  5 5   5    6    5    6    68  68   65   50  8                  __________________________________________________________________________

EXAMPLE 33

The reactivated catalysts as obtained in Example 32 (Catalysts C₂₈ -1,C₂₈ -2 and C₂₈ -5) were each subjected to further treatment forreactivation under the conditions as shown in Table 29. The thusreactivated catalysts were each reused for continuous hydro-crackingunder the same conditions as shown in Table 27. The results are shown inTable 29 (Catalysts E₂₉ -1 to E₂₉ -8).

Likewise, the reactivated catalysts as obtained in Example 32 (CatalystsD₂₈ -1 and D₂₈ -2) were each subjected to further treatment forreactivation under the conditions as shown in Table 29. The thusreactivated catalysts were each reused for continuous hydro-crackingunder the same conditions as shown in Table 27. The results are shown inTable 29 (Catalysts E₂₉ -9 to E₂₉ -12).

As seen from Table 29, the catalyst (E₂₉ -1 to E₂₉ -6 and E₂₉ -9 to E₂₉-12) reactivated in two steps are much more recovered in catalyticactivity than the catalysts reactivated in one step.

                                      Table 29                                    __________________________________________________________________________    Catalyst   E.sub.29 -1                                                                       E.sub.29 -2                                                                       E.sub.29 -3                                                                        E.sub.29 -4                                                                        E.sub.29 -5                                                                       E.sub.29 -6                                                                       E.sub.29 -7                                                                       E.sub.29 -8                                                                       E.sub.29 -9                                                                       E.sub.29 -10                                                                       E.sub.29 -11                                                                      E.sub.29 -12        Catalyst used                                                                            C.sub.28 -1                                                                       C.sub.28 -1                                                                       C.sub.28 -1                                                                        C.sub.28 -1                                                                        C.sub.28 -2                                                                       C.sub.28 -5                                                                       C.sub.28 -1                                                                       C.sub.28 -1                                                                       D.sub.28 -1                                                                       D.sub.28 -2                                                                        D.sub.28 -3                                                                       D.sub.28            __________________________________________________________________________                                                              -4                  Condi-                                                                             Reactivat-                                                                          0.375N                                                                            0.375N                                                                            0.375N                                                                             0.375N                                                                             0.1N                                                                              0.375N                                                                            0.375N                                                                            0.375N                                                                            H.sub.2                                                                           H.sub.2 O:N.sub.2                                                                  H.sub.2                                                                           H.sub.2                                                                       O:N.sub.2           tions                                                                              ing agent                                                                           NaOH                                                                              NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       NaOH                                                                              NaOH                                                                              NaOH                                                                              NaOH    (3:1     (3:1                of                                               by mol)  by mol)             treat-                                                                             Tempera-                                                                            50  80  100  100  100 80  30  30  600 650  600 650                 for  ture (°C.)                                                        reacti-                                                                            Pressure                                                                            1.0 1.0 1.0  1.0  1.0 1.0 1.0 1.0 6.0 6.0  6.0 6.0                 vation                                                                             (ata)                                                                         Time (hrs)                                                                          6.0 1.5 3.0  3.0  1.5 1.5 10.0                                                                              3.0 6.0 12.0 6.0 12.0                Post-treat-                                                                              Water washing: 100° C., 2 hrs.                                                                           --  --   --  --                  ment       Drying: 100° C., 16 hrs.                                    Elimina-                                                                           Carbo-                                                                              79  84  83   81   81  100 78  78  86  100  85  100                 tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                           83  96  94   88   90  97  80  51  89  87   83  80                  materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                    34  41  40   38   40   41 31  30  34  36   32  31                  (m.sup.2 /g-Ru)                                                               Conversion of                                                                            60  78  75   74   75  78  9   7   78  78   75  65                  hydrogen (%)                                                                  __________________________________________________________________________

EXAMPLE 34

The reactivated catalysts as obtained in Example 33 (Catalysts E₂₉ -1,E₂₉ -7 and E₂₉ -8) were each subjected to further treatment forreactivation under the conditions as shown in Table 30. The thusreactivated catalysts were each reused for continuous hydro-crackingunder the same conditions as shown in Table 27. The results are shown inTable 30.

As seen from Table 30, the catalysts (F₃₀ -1 to F₃₀ -11) reactivated inthree steps are more recovered in catalytic activity than the catalystsreactivated in two steps.

                                      Table 30                                    __________________________________________________________________________    Catalyst   F.sub.30 -1                                                                       F.sub.30 -2                                                                        F.sub.30 -3                                                                        F.sub.30 -4                                                                         F.sub.30 -5                                                                        F.sub.30 -6                                                                       F.sub.30 -7                                                                        F.sub.30 -8                                                                        F.sub.30 -9                                                                       F.sub.30 -10                                                                       F.sub.30 -11       Catalyst used                                                                            E.sub.29 -1                                                                       E.sub.29 -1                                                                        E.sub.29 -1                                                                        E.sub.29 -1                                                                         E.sub.29 -1                                                                        E.sub.29 -7                                                                       E.sub.29 -7                                                                        E.sub.29 -7                                                                        E.sub.29 -7                                                                       E.sub.29 7                                                                         E.sub.29           __________________________________________________________________________                                                               -8                 Condi-                                                                             Reactivat-                                                                          0.4%                                                                              0.5% 0.3% 0.3%  0.3% 0.4%                                                                              0.4% 0.3% 0.7%                                                                              2.0% 1.0%               tions                                                                              ing agent                                                                           Hydra-                                                                            Formal-                                                                            Sodium                                                                             Lithium                                                                             Glucose                                                                            Hydra-                                                                            Formal-                                                                            Sodium                                                                             Sodium                                                                            Sodium                                                                             Hydra-             of         zine                                                                              dehyde                                                                             boro-                                                                              aluminum   zine                                                                              dehyde                                                                             boro-                                                                              tartrate                                                                          formate                                                                            zine               treat-              hydride                                                                            hydride             hydride                          ment Tempera-                                                                            20  20   20   20    20   20  20   20   20  20   60                 for  ture (° C.)                                                       reacti-                                                                            Pressure                                                                            1.0 1.0  1.0  1.0   1.0  1.0 1.0  1.0  1.0 1.0  1.0                vation                                                                             (ata)                                                                         Time (hrs)                                                                          3.0 3.0  3.0  3.0   3.0  3.0 3.0  3.0  3.0 3.0  3.0                Post-treat-                                                                              Water washing: 75° C., 3 hrs.                               ment       Drying: 100° C., 16 hrs.                                    Elimina-                                                                           Carbo-                                                                              80  81   81   81    81   80  80   80   80  80   80                 tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                           96  90   95   92    92   92  97   90   91  93   94                 materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                    41  40   40   40    40   37  36   35   36  36   39                 (m.sup.2 /g-Ru)                                                               Conversion of                                                                            75  74   74   75    73   45  44   42   44  44   49                 hydrogen (%)                                                                  __________________________________________________________________________

EXAMPLE 35

A catalyst comprising 0.3% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter (hereinafter referred to as"Catalyst A₃₂ ") (1000 ml ) was charged into a tubular reactor of 1 inchin diameter, and naphtha (content of sulfur, 2 ppm; final boiling point,110° C.) and hydrogen were fed therein to effect continuouslyhydro-cracking reaction for 200 hours under the conditions as shown inTable 31.

                  Table 31                                                        ______________________________________                                        Temperature of                                                                reactor at inlet   265° C.                                             Pressure           46 atm. (absolute)                                         Ratio of hydrogen/                                                            hydrocarbon        1.20 (by mol)                                              Mass velocity      500 kg-mol/m.sup.2 . hr                                    ______________________________________                                    

After 200 hours, the catalyst (hereinafter referred to as "Catalyst B₃₂") was treated under the same conditions as shown in Table 32 forreactivation. The reactivated catalyst was reused in hydro-crackingreaction under the same conditions as mentioned above. The results areshown in Table 32.

As seen from Table 32, treatment with a gaseous material is extremelyeffective in removal of carbonaceous materials but is insufficient inremoval of sulfurous materials. In addition, it is almost ineffective inrecovery of the dispersibility. Thus, recovery of the catalytic activityis not substantially recognized. Treatment with an inorganic alkalinesubstance is effective not only in removal of sulfurous materials andrecovery of the dispersibility but also in recovery of the catalyticactivity.

    Table 32      Reactivated Catalyst A.sub.32 B.sub.32 C.sub.32 -1 C.sub.32 -2 C.sub.32     -3 C.sub.32 -4 C.sub.32 -5 D.sub.32 -1 D.sub.32 -2 D.sub.32 -3 D.sub.32     -4 D.sub.32 -5 D.sub.32 -6 D.sub.32 -7 D.sub.32 -8 D.sub.32      -9             Condi- Reactivating -- -- H.sub.2 H.sub.2 :H.sub.2 O     H.sub.2 O:N.sub.2 O.sub.2 :N.sub.2 O.sub.2 :H.sub.2 O:N.sub.2 0.375N     0.375N 0.375N 0.375N 0.375N 0.375N 0.1N 0.375N 0.375N tions agent     (1:1 by (3:1 by (21:79 by (10:50:40 NaOH NaOH NaOH NaOH Na.sub.2     CO.sub.3 Ba(OH).sub.2 NaOH Na.sub.2 CO.sub.3 Ba(OH).sub.2 of     mol)     mol) volume) by volume) treat- Temperature -- -- 600 600 650 500 600 30     30 50 100 100 100 100 80 100 ment (°  C.) for Pressure -- -- 6.0     6.0 6.0 6.0 6.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 reacti- (ata) vation     Time (hrs) -- -- 6.0 6.0 12.0 5.0 10.0 3.0 10.0 6.0 3.0 3.0 3.0 3.0 3.0     1.5 Post-treat- -- -- -- -- -- -- -- Water washing: 100° C., 2     hrs. ment        Drying: 100° C., 16 hrs. Elimina- Carbo- -- --     76 78 100 100 100 10 30 35 47 43 40 29 37 38 tion per- naceous centage     materials of poisonous Sulfurous -- -- 28 31 34 42 40 40 73 79 90 86 82     76 78 77 materials materials (%) Specific surface area 43 25 25 25 25 23 2     4 27 28 31 36 36 32  30 31 30 (m.sup.2 /g-Ru) Conversion of hydrogen 89     5 5 6 7 5 5 6 8 50 68 68 68 66 65 60 (%)

EXAMPLE 36

The reactivated catalysts as obtained in Example 35 (Catalysts D₃₂ -7,D₃₂ -8 and D₃₂ -9) were each subjected to further treatment forreactivation under the conditions as shown in Table 33. The thusreactivated catalysts were each reused for continuous hydro-crackingunder the same conditions as shown in Table 31. The results are shown inTable 33.

As seen from Table 33, the catalysts reactivated in two steps are muchmore recovered in catalytic activity than the catalysts reactivated inone step.

                                      Tabl3 33                                    __________________________________________________________________________    Catlayst    E.sub.33 -1                                                                       E.sub.33 -2                                                                        E.sub.33 -3                                                                         E.sub.33 -4                                                                       E.sub.33 -5                                    Catalyst used                                                                             D.sub.32 -7                                                                       D.sub.32 -7                                                                        D.sub.32 -7                                                                         D.sub.32 -8                                                                       D.sub.32 -9                                    __________________________________________________________________________    Condi-                                                                             Reactivating                                                                         H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 O.sub.2 :H.sub.2 O:N.sub.2                                                          H.sub.2                                                                           H.sub.2 :H.sub.2 O                             tions                                                                              agent      (1:1 by                                                                            (10:50:40 1:1 by                                         of              mol) by volume)                                                                              mol)                                           treat-                                                                        ment                                                                          for  Temperature                                                                          600 600  600   650 650                                            reacti-                                                                            (° C.)                                                            vation                                                                             Pressure                                                                             6.0 6.0  6.0   6.0 6.0                                                 (ata)                                                                         Time (hrs)                                                                           6.0 6.0  10.0  12.0                                                                              12.0                                                Post-treat-                                                                          --  --   --    --  --                                                  ment                                                                     Elimina-                                                                           Carbo- 83  85   100   100 100                                            tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            80  81   84    81  82                                             materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                     31  31   30    30  30                                             (m.sup.2 /g-Ru)                                                               Conversion of hydrogen                                                                    73  73   73    72  68                                             (%)                                                                           __________________________________________________________________________

EXAMPLE 37

The reactivated catalysts as obtained in Example 35 (Catalysts D₃₂ -1 toD₃₂ -5 and D₃₂ -9) were each subjected to further treatment forreactivation under the conditions as shown in Table 34. The thusreactivated catalysts were each reused for continuous hydro-crackingunder the same conditions as shown in Table 31. The results are shown inTable 34.

As seen from Table 34, the catalysts reactivated in two steps are muchmore recovered in catalytic activity than the catalysts reactivated inone step.

                                      Table 34                                    __________________________________________________________________________    Catalyst    F.sub.34 -1                                                                        F.sub.34 -2                                                                        F.sub.34 -3                                                                         F.sub.34 -4                                                                        F.sub.34 -5                                                                        F.sub.34 -6                                                                        F.sub.34 -7                                                                        F.sub.34 -8                                                                        F.sub.34 -9                                                                        F.sub.34 -10        Catalyst used                                                                             D.sub.32 -1                                                                        D.sub.32 -2                                                                        D.sub.32 -3                                                                         D.sub.32 -3                                                                        D.sub.32 -3                                                                        D.sub.32 -4                                                                        D.sub.32 -8                                                                        D.sub.32 -8                                                                        D.sub.32 -9                                                                        D.sub.32            __________________________________________________________________________                                                              -9                  Condi-                                                                             Reactivating                                                                         1.0% 0.4% 0.3%  0.5% 0.3% 0.3% 0.5% 0.7% 0.4% 2.0%                tions                                                                              agent  Hydra-                                                                             Hydra-                                                                             Lithium                                                                             Formal-                                                                            Sodium                                                                             Glucose                                                                            Formal-                                                                            Sodium                                                                             Hydra-                                                                             Sodium              of          zine zine aluminum                                                                            dehyde                                                                             boro-     dehyde                                                                             tartrate                                                                           zine formate             treat-                hydride    hydride                                      ment Temperature                                                                          60   20   20    20   20   20   20   20   20   20                  for  (° C.)                                                            reacti-                                                                            Pressure                                                                             1.0  1.0  1.0   1.0  1.0  1.0  1.0  1.0  1.0  1.0                 vation                                                                             (ata)                                                                         Time (hrs)                                                                           3.0  3.0  3.0   3.0  3.0  3.0  3.0  3.0  3.0  3.0                 Post-treat- Water washing: 75° C., 3 hrs.                              ment        Drying: 100° C., 16 hrs.                                   Elimina-                                                                           Carbo- 10   30   35    35   35   47   37   37   38   38                  tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            90   91   95    95   95   98   90   89   92   90                  materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                     37   38   38    38   37   41   38   38   38   38                  (m.sup.2 /g-Ru)                                                               Conversion of hydrogen                                                                    70   70   71    68   70   71   70   70   71   72                  (%)                                                                           __________________________________________________________________________

EXAMPLE 38

The reactivated catalysts as obtained in Example 37 (Catalysts F₃₄ -1,F₃₄ -3 and F₃₄ -5 to F₃₄ -7) were each subjected to further treatmentfor reactivation under the conditions as shown in Table 35. The thusreactivated catalysts were each reused for continuous hydro-crackingunder the same conditions as shown in Table 31. The results are shown inTable 35.

As seen from Table 35, the catalysts (G₃₅ -1 to G₃₅ -5) reactivated inthree steps are much more recovered in catalytic activity than thecatalysts reactivated in two step.

                                      Table 35                                    __________________________________________________________________________    Catalyst    G.sub.35 -1                                                                       G.sub.35 -2                                                                       G.sub.35 -3                                                                        G.sub.35 -4                                                                        G.sub.35 -5                                     Catalyst used                                                                             F.sub.34 -1                                                                       F.sub.34 -3                                                                       F.sub.34 -5                                                                        F.sub.34 -6                                                                        F.sub.34 -7                                     __________________________________________________________________________    Condi-                                                                             Reactivating                                                                         H.sub.2                                                                           H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 H.sub.2 O:N.sub.2                                                                  O.sub.2 :H.sub.2 O:N.sub.2                      tions                                                                              agent          (1:1 by                                                                            (3:1 by                                                                            (10:50:40                                       of                  mol) mol) by volume)                                      treat-                                                                        ment                                                                          for  Temperature                                                                          650 600 600  650  600                                             reacti-                                                                            (° C.)                                                            vation                                                                             Pressure                                                                             6.0 6.0 6.0  6.0  6.0                                                  (ata)                                                                         Time (hrs)                                                                           12.0                                                                              6.0 6.0  12.0 10.0                                                 Post-treat-                                                                          --  --  --   --   --                                                   ment                                                                     Elimina-                                                                           Carbo- 100 84  85   100  100                                             tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            96  97  97   97   96                                              materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                     38  39  38   41   39                                              (m.sup.2 /g-Ru)                                                               Conversion of hydrogen                                                                    77  78  76   79   78                                              (%)                                                                           __________________________________________________________________________

EXAMPLE 39

The reactivated catalysts (Catalysts E₃₃ -1 and G₃₅ -4) respectively asobtained in Examples 36 and 38 were reused for continuous hydro-crackingunder the conditions as shown in Table 31. The reactivated catalystsshowed the same tendency as a freshly prepared catalyst (Catalyst A₃₂)in depression of the catalytic activity.

EXAMPLE 40

A catalyst comprising 0.3% of platinum deposited on spheroidal particlesof alumina of 4 mm in diameter as a carrier material (hereinafterreferred to as "Catalyst A₃₇ ") (1000 ml) was charged into a tubularreactor of 1 inch in diameter, and a gaseous mixture comprising naphtha(content of sulfur, 2 ppm; final boiling point, 105° C.) and hydrogenwas fed therein to effect continuous hydro-cracking reaction for 200hours under the conditions as shown in Table 36.

                  Table 36                                                        ______________________________________                                        Temperature of                                                                reactor at inlet   260° C.                                             Pressure           46 atm. (absolute)                                         Ratio of hydrogen/                                                            hydrocarbon        1.4 (by mol)                                               Mass velocity      500 kg-mol/m.sup.2 . hr                                    ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₃₇ ") was treated under the conditions as shown in Table 37for reactivation. The reactivated catalyst was reused in hydro-crackingreaction under the same conditions as mentioned above. The results areshown in Table 37.

As seen from Table 37, the reactivation treatment with hydrogen orhydrogen-steam is extremely effective for elimination of carbonaceousmaterials, but removal of sulfurous materials is insufficient and thedispersibility can be hardly recovered so that recovery of the catalyticactivity is scarcely observed (Catalysts C₃₇ -1 and C₃₇ -2). In the caseof treatment with an inorganic alkaline substance at room temperaturefor a long time, elimination of sulfurous materials and recovery of thedispersibility are good, but recovery of the catalytic activity is notwell recognized (Catalysts D₃₇ -1 and D₃₇ -2). When treated with aninorganic alkaline substance under heating, the catalytic activity ishighly recovered.

                                      Table 37                                    __________________________________________________________________________                      Reactivated                                                 Catalyst    A.sub.37                                                                         B.sub.37                                                                         C.sub.37 -1                                                                       C.sub.37 -2                                                                        D.sub.37 -1                                                                       D.sub.37 -2                                                                       D.sub.37 -3                                                                       D.sub.37 -4                                                                        D.sub.37 -5                       __________________________________________________________________________    Condi-                                                                             Reactivating H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 0.375N                                                                            0.375N                                                                            0.375N                                                                            0.375N                                                                             0.375N                            tions                                                                              agent*)                                                                              -- --     (1:1 by                                                                            NaOH                                                                              NaOH                                                                              NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                      of                    mol)                                                    treat                                                                              Temperature                                                              ment (° C.)                                                                        -- -- 600 600  30  50  100 100  100                               for  Pressure                                                                 reacti-                                                                            (ata)  -- -- 6.0 6.0  1.0 1.0 1.0 1.0  1.0                               vation                                                                             Time (hrs)                                                                           -- -- 6.0 6.0  10.0                                                                              6.0 1.5 3.0  3.0                               Post-treat- -- -- --  --   Water washing: 100° C., 2 hrs.              ment                       Drying: 100° C., hrs.                       Elimina-                                                                           Carbo- -- -- 76  78   30  35  44  43   40                                tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                materials                                                                          materials                                                                            -- -- 26  31   73  79  88  86   82                                (%)                                                                           Specific surface area                                                         (m.sup.2 /g-Ru)                                                                           42 24 24  25   27  30  34  37   32                                Conversion of hydrogen                                                        (%)         85  5 7   6    5   50  68  69   69                                __________________________________________________________________________

EXAMPLE 41

A catalyst comprising 1.0% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter as a carrier material(hereinafter referred to as "Catalyst A₃₉ ") (250 ml) was charged into atubular reactor of 1 inch in diameter, and a gaseous mixture comprisingmethanol (content of sulfur, 1 ppm) and hydrogen was fed therein toeffect continuously hydro-cracking reaction for 200 hours under theconditions as shown in Table 38.

                  Table 38                                                        ______________________________________                                        Temperature of                                                                reactor at inlet   470° C.                                             Pressure           10 atm. (absolute)                                         Ratio of hydrogen/                                                            methanol           1.1 (by mol)                                               Mass velocity      500 kg-mol/m.sup.2 . hr                                    ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₃₉ ") was treated under the conditions as shown in Table 39for reactivation. The reactivated catalyst was reused in hydro-crackingreaction under the same conditions as mentioned above. The results areshown in Table 39.

As seen from Table 39, the reactivation treatment with hydrogen orhydrogen-steam is extremely effective for elimination of carbonaceousmaterials, but removal of sulfurous materials is insufficient and thedispersibility can be hardly recovered so that recovery of the catalyticactivity is scarcely observed (Catalysts C₃₉ -1 and C₃₉ -2). In the caseof treatment with an inorganic alkaline substance at room temperaturefor a long time, elimination of sulfurous materials and recovery of thedispersibility are good, but recovery of the catalytic activity is notwell recognized (Catalysts D₃₉ -1 and D₃₉ -2). When treated with aninorganic alkaline substance under heating, the catalytic activity ishighly recovered (Catalysts D₃₉ -3 to D₃₉ -5). Sole treatment with anaqueous solution of a reducing substance is effective in elimination ofsulfurous materials but not in elimination of carbonaceous materials.Nevertheless, a tendency to recovery of the catalytic activity is seen(Catalysts D₃₉ -6 to D₃₉ -8).

                                      Table 39                                    __________________________________________________________________________                      Reactivated                                                 Catalyst    A.sub.39                                                                         B.sub.39                                                                         C.sub.39 -1                                                                       C.sub.39 -2                                                                        D.sub.39 -1                                                                       D.sub.39 -2                                                                       D.sub.39 -3                                                                       D.sub.39 -4                                                                        D.sub.39 -5                                                                        D.sub.39 -6                                                                        D.sub.39 -7                                                                       D.sub.39            __________________________________________________________________________                                                              -8                  Condi-                                                                             Reactivating H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 0.375N                                                                            0.375N                                                                            0.375N                                                                            0.375N                                                                             0.375N                                                                             0.4% 0.3%                                                                              1.0%                tions                                                                              agent  -- --     (1:1 by                                                                            NaOH                                                                              NaOH                                                                              NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       Hydra-                                                                             Glu-                                                                              Form-               of                    mol)                       zine cose                                                                              alde-               treat-                                                    hyde                ment Temperature                                                              for  (° C.)                                                                        -- -- 600 600  30  50  100 100  100  20   20  60                  reacti-                                                                            Pressure                                                                 vation                                                                             (ata)  -- -- 6.0 6.0  1.0 1.0 1.0 1.0  1.0  1.0  1.0 1.0                      Time (hrs)                                                                           -- -- 6.0 6.0  10.0                                                                              6.0 1.5 3.0  3.0  3.0  3.0 3.0                 Post-treat- -- -- --  --   Water washing: 100° C., 2                                                                    Water washing:                                                                75° C., 3 hrs.        ment                       Drying: 100° C., 16 hrs.                                                                     Drying: 100° C.,                                                       16 hrs.                      Elimina-                                                                           Carbo- -- -- 75  76   10  35  45  43   40   0    0   0                   tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                            -- -- 24  25   40  80  89  85   84   70   51  69                  materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                         (mg.sup.2 /g-Ru)                                                                          42 18 18  18   22  26  31  30   28   26   27  27                  Amount of catalyst                                                            required (ml)                                                                             80 -- --  --   200 148 120 122  130  152  151 150                 __________________________________________________________________________

EXAMPLE 42

The reactivated catalysts as obtained in Example 41 (Catalysts D₃₉ -1 toD₃₉ -4) were each subjected to further treatment for reactivation underthe conditions as shown in Table 40. The thus reactivated catalysts wereeach reused for continuous hydro-cracking under the same conditions asshown in Table 38. The results are shown in Table 40.

As seen from Table 40, the catalysts (E₄₀ -1 to E₄₀ -5) are effectivelyrecovered in catalytic activity.

                  Table 40                                                        ______________________________________                                        Catalyst    E.sub.40 -1                                                                           E.sub.40 -2                                                                           E.sub.40 -3                                                                         E.sub.40 -4                                                                          E.sub.40 -5                          Catalyst used                                                                             D.sub.39 -1                                                                           D.sub.39 -2                                                                           D.sub.39 -3                                                                         D.sub.39 -3                                                                          D.sub.39 -4                          ______________________________________                                        Condi- Reacti-  1.0%    0.4%  0.4%  0.5%   0.4%                               tions  vating   Hydra-  Hydra-                                                                              Hydra-                                                                              Formal-                                                                              Hydra-                             of     agent    zine    zine  zine  dehyde zine                               treat- Tempera- 60      20    20    20     20                                 ment   ature                                                                  for    (° C.)                                                          reacti-                                                                              Pressure 1.0     1.0   1.0   1.0    1.0                                vation (ata)                                                                         Time                                                                          (hrs)    3.0     3.0   3.0   3.0    3.0                                Post-       Water washing: 75° C., 3 hrs.                              treat-      Drying: 100° C., 16 hrs.                                   ment                                                                          Elimina-                                                                             Carbo-   10      35    45    45     43                                 tion per-                                                                            naceous                                                                centage                                                                              materials                                                              of                                                                            poisonous                                                                            Sulfurous                                                                              90      94    96    98     96                                 materials                                                                            materials                                                              (%)                                                                           Specific surface area                                                                     30      32      35    35     34                                   (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                        122     110     95    95     98                                   required (ml)                                                                 ______________________________________                                    

EXAMPLE 43

A catalyst comprising 1.5% of ruthenium and 0.1% of chromium oxidedeposited on spheroidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₄₁ ") (290 ml)was charged into a tubular reactor of 1 inch in diameter, and a gaseousmixture comprising methane and air was fed therein to effectcontinuously partial combustion reaction for 500 hours under thefollowing conditions:

Temperature of reactor: inlet, 310° C., outlet, 700° C;

Space velocity: 17500 (1/hr);

Ratio of air/methane: 2.37 (by mol);

Pressure: 1 atm. (absolute)

After 500 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₄₁ ") was treated under the conditions as shown in Table 41for reactivation. The reactivated catalyst was reused in partialcombustion reaction under the same conditions as mentioned above. Theresults are shown in Table 41.

As seen from Table 41, the reactivation treatment with hydrogen isextremely effective for elimination of carbonaceous materials, butremoval of sulfurous materials is insufficient and the dispersibilitycan be hardly recovered so that recovery of the catalytic activity isscarcely observed (Catalyst C₄₁ -1). In the case of treatment with aninorganic alkaline substance at room temperature for a long time,elimination of sulfurous materials and recovery of the dispersibilityare good, but recovery of the catalytic activity is not well recognized(Catalysts D₄₁ -1 and D₄₁ -2). Treatment with an inorganic alkalinesubstance under heating is per se effective in recovery of the catalyticactivity (Catalysts D₄₁ -3 to D₄₁ -5 and D₄₁ -14 to D₄₁ -16). Treatmentwith an aqueous solution of a reducing substance is effective inelimination of sulfurous materials but not in elimination ofcarbonaceous materials and recovery of the dispersibility. Nevertheless,a tendency to recovery of the catalytic activity is seen (Catalysts D₄₁-6 to D₄₁ -13).

    Table 41      Reactivated Catalyst A.sub.41 B.sub.41 C.sub.41 -1 D.sub.41 -1 D.sub.41     -2 D.sub.41 -3 D.sub.41 -4 D.sub.41 -5 D.sub.41 -6 D.sub.41 -7 D.sub.41     -8 D.sub.41 -9 D.sub.41 -10 D.sub.41 -11 D.sub.41 -12 D.sub.41 -13     D.sub.41 -14 D.sub.41 -15 D.sub.41      -16                                     Condi- Reactivating   H.sub.2     0.375N 0.375N 0.375N 0.375N 0.375N 0.4% 0.3% 0.7% 2.0% 0.3% 1.0% 1.0%     1.0% 3.0N 0.375N 0.375N tions agent -- --  NaOH NaOH NaOH NaOH NaOH     Hydra- Lithium Sodium Sodium Glu- Hydra- Form- Sodium NaOH Na.sub.2     CO.sub.3 Ba(OH).sub.2 of          zine aluminum tart- for- cose zine     alde- borohy- treat-           hydride rate mate   hyde dride ment     Temperature for (° C.) -- -- 650  30 30 50 100 148 20 20 20 20 20 6     0 60 60 100 100 100 reacti- Pressure vation (ata) -- -- 6.0 1.0 1.0 1.0     1.0 5.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  Time (hrs) -- --     12.0 3.0 10.0 6.0 3.0 1.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0     Post-treat- -- -- -- Water washing: 100° C., 2 hrs. Water     washing: 75° C. 3 hrs. Water washing: 75° C., 3 hrs. Water     washing: 100° C., 2 hrs. ment    Drying: 100° C., 16 hrs.     Drying 100° C., 16 hrs Drying: 100° C., 16 hrs. Drying:     100° C., 16 hrs. Elimina- Carbo- -- -- 100 12 41 43 52 58 0 0 0 0 0      0 0 0 54 50 48 tion per- naceous centage materials of poisonous     Sulfurous -- -- 31 32 72 78 95 100 70 51 50 55 51 92 70 90 97 94 91     materials materials (%) Specific surface area     (m.sup.2 /g-Ru) 43 17 17 21 26 28 33 34 19 21 21 21 21 21 21 21 34 32 30     Amount of catalyst required (ml) 51 -- -- -- -- 150 105 100 174 170 172     172 174 166 170 174 101 107 110

EXAMPLE 44

The reactivated catalysts as obtained in Example 43 (Catalysts D₄₁ -1 toD₄₁ -13) were each subjected to further treatment for reactivation underthe conditions as shown in Table 42. The thus reactivated catalysts wereeach reused for continuous partial combustion under the same conditionsas shown in Example 43. The results are shown in Table 42.

As seen from Table 42, the treatment for reactivation at the second stepis quite effective for recovery of the catalytic activity.

    Table 42      Catalyst  E.sub.42 -1 E.sub.42 -2 E.sub.42 -3 E.sub.42 -4 E.sub.42 -5     E.sub.42 -6 E.sub.42 -7 E.sub.42 -8 E.sub.42 -9 E.sub.42 -10 E.sub.42     -11 E.sub.42 -12 E.sub.42 -13 E.sub.42 -14 E.sub.42 -15 E.sub.42 -16     E.sub.42 -17 E.sub.42 -18 E.sub.42 -19 E.sub.42 -20 Catalyst used     D.sub.41 -1 D.sub.41 -2 D.sub.41 -3 D.sub.41 -3 D.sub.41 -4 D.sub.41 -4     D.sub.41 -6 D.sub.41 -6 D.sub.41 -11 D.sub.41 -12 D.sub.41 -1 D.sub.41     -2 D.sub.41 -3 D.sub.41 -3 D.sub.41 -4 D.sub.41 -4 D.sub.41 -7 D.sub.41     -8 D.sub.41 -9 D.sub.41      -9                                                 Condi- Reactivating     1.0% 0.4% 0.4% 0.5% 0.4% 0.3% 0.375N 0.375N 0.375N 0.375N 0.3% 0.3% 0.7% 2     .0% 0.3% 0.3% 0.375N 0.1N 0.375N 0.375N tions agent Hydra- Hydra- Hydra-     For- Hydra- Sodium NaOH NaOH NaOH NaOH Lithium Lithium Sodium Sodium     Lithium Glu- NaOH NaOH NaOH NaOH of  zine zine zine mal- zine boro-     alu- alu- tart- for- alu- cose treat-     dehyde  hy-     minum minum     rate mate minum ment       dride     hydride hydride   hydride for     Temperature 60 20 20 20 20 20 50 100 100 80 20 20 20 20 20 20 50 100 100 8     0 reacti- (° C.) vation Pressure 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0     1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  (ata)  Time (hrs) 3.0     3.0 3.0 3.0 3.0 3.0 6.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 6.0 3.0 1.5     3.0 Post-treat- Water washing: 75° C., 3 hrs. Water Washing:     100° C., 2 hrs. Water washing: 75° C., 3 hrs. Water     washing: 100° C., 2 hrs. ment Drying: 100° C., 16 hrs.     Drying: 100° C., 16 hrs. Drying: 100° C., 16 hrs. Drying:     100° C., 16 hrs. Elimina- Carbo- 12 41 43 43 52 52 43 54 53 47 12 4     1 43 43 52 52 43 44 46 47 tion per- naceous centage materials of     poisonous Sulfurous 91 93 95 95 97 96 92 97 96 92 68 88 91 92 96 96 91     90 94 93 materials materials (%) Specific surface area 34 36 36 36 40 40 3     5 39 41 39 31 36 37 37 41 40 38 37 37 37 (m.sup.2 /g-Ru) Amount of     catalyst 150 160 101 105 75 77 103 76 74 90 149 154 102 110 76 77 115 72     80 92 required (ml)

EXAMPLE 45

The reactivated catalyst as obtained in Example 43 (Catalyst D₄₁ -3) wastreated with a 0.7% aqueous solution of sodium tartrate at 20° C. under1 atom. (absolute) for 3 hours, washed with water at 75° C. for 3 hoursand dried at 100° C. for 16 hours. Then, the resulting catalyst wasagain subjected to treatment with a 0.375 N aqueous solution of sodiumhydroxide at 50° C. under 1 atom. (absolute) for 6 hours and treatmentwith a 0.7% aqueous solution of sodium tartrate at 20° C. under 1 atom.(absolute) for 3 hours, followed by washing with water at 75° C. for 3hours and drying at 100° C. for 16 hours. The thus reactivated catalystwas used for partial combustion under the same conditions as shown inExample 43. The results are shown in Table 43, from which it isunderstood that the repeating treatments are quite effective in recoveryof the catalytic activity.

                  Table 43                                                        ______________________________________                                        Catalyst                 F                                                    ______________________________________                                        Elimination   Carbonaceous                                                    percentage    materials      75                                               of poison-                                                                    ous mate-     Sulfurous                                                       rials (%)     materials      100                                              Specific surface area                                                         (m.sup.2 /g-Ru)          42                                                   Amount of catalyst required                                                   (ml)                     58                                                   ______________________________________                                    

EXAMPLE 46

The reactivated catalyst as obtained in Example 44 (Catalyst E₄₂ -5) wasused for continuous partial combustion under the conditions as shown inExample 43. The reactivated catalyst showed the same tendency as afreshly prepared catalyst in depression of the catalytic activity.

EXAMPLE 47

A catalyst comprising 1.7% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter as a carrier material(hereinafter referred to as "Catalyst A₄₅ ") (290 ml) was charged into atubular reactor of 1 inch in diameter, and a gaseous mixture comprisingmethane and air was fed therein to effect continuously partialcombustion reaction for 300 hours under the conditions as shown in Table44.

                  Table 44                                                        ______________________________________                                        Temperature of   at inlet   310° C.                                    reactor          at outlet  700° C.                                    Space velocity          17500 hr.sup.-1                                       Ratio of air/methane    2.37 (by mol)                                         Pressure                1 atm.                                                                        (absolute)                                            ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₄₅ ") was treated under the conditions as shown in Table 45for reactivation. The reactivated catalyst was reused in partialcombustion reaction under the same conditions as mentioned above. Theresults are shown in Table 45.

As seen from Table 45, the reactivation treatment with a gaseousmaterial such as hydrogen, hydrogen-steam, oxygen-nitrogen oroxygen-nitrogen-steam is extremely effective for elimination ofcarbonaceous materials, but removal of sulfurous materials isinsufficient and the dispersibility can be hardly recovered so thatrecovery of the catalytic activity is scarcely observed (Catalysts C₄₅-1 to C₄₅ -5). In the case of treatment with an inorganic alkalinesubstance at room temperature, elimination of sulfurous materials isgood but recovery of the catalytic activity is not seen. Treatment withan inorganic alkaline substance under heating is effective inelimination of sulfurous materials and recovery of the dispersibility,and recovery of the catalytic activity is recognized.

                                      Table 45                                    __________________________________________________________________________                     Reactivated                                                  Catalyst   A.sub.45                                                                         B.sub.45                                                                         C.sub.45 -1                                                                      C.sub.25 -2                                                                        C.sub.45 -3                                                                        C.sub.45 -4                                                                        C.sub.45 -5                                                                         D.sub.45 -1                                                                       D.sub.45 -2                                                                        D.sub.45 -3                                                                        D.sub.45 -4                                                                       D.sub.45           __________________________________________________________________________                                                               -5                 Condi-                                                                             Reacti-                                                                             -- -- H.sub.2                                                                          H.sub.2 :H.sub.2 O                                                                 H.sub.2 O:N.sub.2                                                                  O.sub.2 :N.sub.2                                                                   O.sub.2 :H.sub.2 O:N.sub.2                                                          0.375N                                                                            0.375N                                                                             0.375N                                                                             0.375N                                                                            0.375N             tions                                                                              vating         (1:1 by                                                                            (3:1 by                                                                            (21:79 by                                                                          (10:50:40                                                                           NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       NaOH                                                                              NaOH               of   agent          mol) mol) volume                                                                             by volume                                  treat-                                                                             Temperature                                                                         -- -- 600                                                                              600  650  500  600   100 100  100  50  30                 ment (°C.)                                                             for  Pressure                                                                            -- -- 6.0                                                                              6.0  6.0  6.0  6.0   1.0 1.0  1.0  1.0 1.0                reacti-                                                                            (ata)                                                                    vation                                                                             Time (hrs)                                                                          -- -- 6.0                                                                              6.0  12.0 5.0  10.0  1.5 3.0  3.0  6.0 10.0               Post-treat-                                                                              -- -- -- --   --   --   --    Water washing: 100° C., 2                                              hrs.                                 ment                                     Drying: 100° C., 16 hrs.      Elimina-                                                                           Carbo-                                                                              -- -- 78   80 100  100  100    55 54   50   41  40                 tion per-                                                                          naceous                                                                  centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                           -- -- 23  30  34    42  40     97 95   89   80  77                 materials                                                                          materials                                                                (%)                                                                           Specific surface area                                                                    43 19 19  19  19    17  18     35 36   33   28  28                 (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                       65 -- -- --   --   --   --    108 101  110  150 --                 required (ml)                                                                 __________________________________________________________________________

EXAMPLE 48

The reactivated catalysts as obtained in Example 47 (Catalysts C₄₅ -1,C₄₅ -2 and C₄₅ -5) were each subjected to further treatment forreactivation under the conditions as shown in Table 46. The thusreactivated catalysts (Catalysts E₄₆ -1 to E₄₆ -7) were each reused forcontinuous partial combustion under the same conditions as shown inTable 44. The results are shown in Table 46, from which it is understoodthat the treatment with an inorganic alkaline substance under heating atthe second step is quite effective in recovery of the catalyticactivity.

                                      Table 46                                    __________________________________________________________________________    Catalyst     E.sub.46 -1                                                                        E.sub.46 -2                                                                        E.sub.46 -3                                                                        E.sub.46 -4                                                                        E.sub.46 -5                                                                        E.sub.46 -6                                                                        E.sub.46 -7                        Catalyst used                                                                              C.sub.45 -1                                                                        C.sub.45 -1                                                                        C.sub.45 -1                                                                        C.sub.45 -1                                                                        C.sub.45 -2                                                                        C.sub.45 -5                                                                        C.sub.45 -1                        __________________________________________________________________________    Condi-                                                                              Reactivating                                                                         0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.1N 0.375N                                                                             0.375N                             tions agent  NaOH NaOH NaOH Ba(OH).sub.2                                                                       NaOH NaOH NaOH                               of                                                                            treat-                                                                        ment                                                                          for   Temperature                                                                          50   80   100  100  100  80   30                                 reacti-                                                                             (°C.)                                                            vation                                                                              Pressure                                                                             1.0  1.0  1.0  1.0  1.0  1.0  1.0                                      (ata)                                                                         Time (hrs)                                                                           3.0  1.5  1.5  2.0  1.5  1.5  10.0                               Post-treat-  Water washing: 100° C., 2 hrs.                            ment         Drying: 100° C., 16 hrs.                                  Elimina-                                                                            Carbo- 81   86   85   83   83   100  80                                 tion per-                                                                           naceous                                                                 centage                                                                             materials                                                               of                                                                            poisonous                                                                           Sulfurous                                                                            85   98   96   90   92   99   82                                 materials                                                                           materials                                                               (%)                                                                           Specific surface area                                                                      31   38   37   37   37   38   28                                 (m.sup. 2 /g-Ru)                                                              Amount of catalyst                                                                         142  115  101  106  117  120  --                                 required (ml)                                                                 __________________________________________________________________________

EXAMPLE 49

The reactivated catalysts as obtained in Example 48 (Catalyst E₄₆ -1)were each subjected to further treatment for reactivation under theconditions as shown in Table 47. The thus reactivated catalysts(Catalysts F₄₇ -1 to F₄₇ -5) were each reused for continuous partialcombustion under the same conditions as shown in Table 44. The resultsare shown in Table 47, from which it is understood that the treatmentfor reactivation in three steps results in higher recovery of thecatalytic activity.

                                      Table 47                                    __________________________________________________________________________     Catalyst    F.sub.47 -1                                                                        F.sub.47 -2                                                                        F.sub.47 -3                                                                        F.sub.47 -4                                                                        F.sub.47 -5                                  Catalyst used                                                                              E.sub.46 -1                                                                        E.sub.46 -1                                                                        E.sub.46 -1                                                                        E.sub.46 -1                                                                        E.sub.46 -1                                  __________________________________________________________________________    Condi-                                                                              Reactivating                                                                         0.4% 0.5% 0.3% 0.3% 0.3%                                         tions agent  Hydra-                                                                             Form-                                                                              Sodium                                                                             Lithum                                                                             Glucose                                      of           zine alde-                                                                              boro-                                                                              aluminium                                         treat-            hyde hydride                                                                            hydride                                           ment  Temperature                                                                          20   20   20   20   20                                           for   (°C.)                                                            reacti-                                                                             Pressure                                                                             1.0  1.0  1.0  1.0  1.0                                          vation                                                                              (ata)                                                                         Time (hrs)                                                                           3.0  3.0  3.0  3.0  3.0                                          Post-treat-    Water washing: 75° C., 3 hrs.                           ment           Drying: 100° C., 16 hrs.                                Elimina-                                                                            Carbo- 82   82   82   82   82                                           tion per-                                                                           naceous                                                                 centage                                                                             materials                                                               poisonous                                                                           Sulfurous                                                                            98   92   97   94   94                                           materials                                                                           materials                                                               (%)                                                                           Specific surface area                                                                      40   39   39   39   39                                           (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                         70   72   72   70   72                                           required (ml)                                                                 __________________________________________________________________________

EXAMPLE 50

A catalyst comprising 1.0% of ruthenium and 0.1% of chromium oxidedeposited on spheroidal particles of alumina of 4 mm in diameter as acarrier material (hereinafter referred to as "Catalyst A₄₉ ") (290 ml)was charged into a tubular reactor of 1 inch in diameter, and a gaseousmixture comprising methane and air was fed therein to effectcontinuously partial combustion reaction for 300 hours under theconditions as shown in Table 48.

                  Table 48                                                        ______________________________________                                        Temperature of   at inlet   310° C.                                    reactor          at outlet  700° C.                                    Space velocity              17500 hr.sup.-1                                   Ratio of air/methane        2.37 (by mol)                                     Pressure                    1 atm.                                                                        (absolute)                                        ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₄₉ ") was treated under the conditions as shown in Table 49for reactivation. The reactivated catalyst was reused in partialcombustion reaction under the same conditions as mentioned above. Theresults as shown in Table 49.

As seen from Table 49, the reactivation treatment with a gaseousmaterial is extremely effective for elimination of carbonaceousmaterials, but removal of sulfurous materials is insufficient and thedispersibility can be hardly recovered so that recovery of the catalyticactivity is scarcely observed. In the case of treatment with aninorganic alkaline substance, elimination of sulfurous materials andrecovery of the dispersibility as well as recovery of the catalyticactivity are good.

                                      Table 49                                    __________________________________________________________________________                        Reactivated                                               Catalyst      A.sub.49                                                                         B.sub.49                                                                         C.sub.49 -1                                                                       C.sub.49 -2                                                                         D.sub.49 -1                                                                        D.sub.49 -2                                                                        D.sub.49 -3                           __________________________________________________________________________    Condi-                                                                              Reactivating  H.sub.2                                                                           O.sub.2 :H.sub.2 O:                                                                 0.375N                                                                             0.1N 0.375N                                tions agent   -- --     N.sub.2 (10:                                                                        NaOH NaOH Na.sub.2 CO.sub.3                     of                      50:40 by                                              treat-                  volume)                                               ment  Temperature                                                                           -- -- 600 600   50   100  100                                   for   (°C.)                                                            reacti-                                                                             Pressure                                                                              -- -- 6.0 6.0   1.0  1.0  1.0                                   vation                                                                              (ata)                                                                         Time (hrs)                                                                            -- -- 6.0 10.0  6.0  3.0  3.0                                         Post-treat-                                                                           -- -- --  --    Water washing: 100° C., 2 hrs.                 ment                    Drying: 100° C., 16 hrs.                 Elimina-                                                                      tion per-                                                                           Carbo-                                                                  centage                                                                             naceous -- -- 75  100   43   40   51                                    of    materials                                                               poisonous                                                                           Sulfurous                                                                             -- -- 21  37    78   80   93                                    materials                                                                           materials                                                               (%)                                                                           Specific surface area                                                                       43 17 17  17    28   28   33                                    (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                          83 -- --  --    140  120  115                                   required (ml)                                                                 __________________________________________________________________________

EXAMPLE 51

The reactivated catalyst as obtained in Example 50 (Catalyst D₄₉ -2) wassubjected to further treatment for reactivation under the conditions asshown in Table 50. The thus reactivated catalyst was reused forcontinuous partial combustion under the same conditions as shown inTable 48. The results are shown in Table 50, from which is understoodthat the catalyst reactivated in two steps is more recovered incatalytic activity than the catalyst reactivated in one step.

                  Table 50                                                        ______________________________________                                        Catalyst           E.sub.50 -1                                                                             E.sub.50 -2                                      Catalyst used      D.sub.49 -2                                                                             D.sub.49 -2                                      ______________________________________                                                  Reactivating H.sub.2   O.sub.2 :H.sub.2 O:N.sub.2                   Condi-    agent                  (10:50:40                                    tions                            by volume)                                   of        Temperature  600       600                                          treat-    (°C.)                                                        ment      Pressure     6.0       6.0                                          for       (ata)                                                               reacti-   Time (hrs)   6.0       10.0                                         vation    Post-treat-  --        --                                                     ment                                                                Elimina-                                                                      tion per- Carbo-       85        100                                          centage   naceous                                                             of        materials                                                           poisonous Sulfurous    85        89                                           materials materials                                                           (%)                                                                           Specific surface area                                                                            29        28                                               (m.sup.2 /g-Ru)                                                               Amount of catalyst 115       114                                              required (ml)                                                                 ______________________________________                                    

EXAMPLE 52

The reactivated catalyst as obtained in Example 50 (Catalysts D₄₉ -1 andD₄₉ -3) was subjected to further treatment for reactivation under theconditions as shown in Table 51. The thus reactivated catalyst wasreused for continuous partial combustion under the same conditions asshown in Table 48. The results are shown in Table 51, from which it isunderstood that the catalyst reactivated in two steps is more recoveredin catalytic activity than the catalyst reactivated in one step.

                  Table 51                                                        ______________________________________                                        Catalyst        F.sub.51 -1                                                                            F.sub.51 -2                                                                            F.sub.51 -3                                 Catalyst used   D.sub.49 -1                                                                            D.sub.49 -1                                                                            D.sub.49 -3                                 ______________________________________                                        Condi-  Reactivating                                                                              0.3%     0.3%   0.3%                                      tions   agent       Lithium  Sodium Glucose                                   of                  aluminum boro-                                            treat-              hydride  hydride                                          ment                                                                          for     Temperature 20       20     20                                        reacti- (° C.)                                                         vation  Pressure    1.0      1.0    1.0                                               (ata)                                                                         Time (hrs)  3.0      3.0    3.0                                               Post-treat- Water washing: 75° C., 3 hrs.                              ment        Drying: 100° C., 16 hrs.                           Elimina-                                                                              Carbo-      43       43     52                                        tion per-                                                                             naceous                                                               centage materials                                                             of                                                                            poisonous                                                                             Sulfurous   96       96     97                                        materials                                                                             materials                                                             (%)                                                                           Specific surface area                                                                         34       32       38                                          (m.sup.2 /g-Ru                                                                Amount of catalyst                                                                            94       97       90                                          required (ml)                                                                 ______________________________________                                    

EXAMPLE 53

The reactivated catalyst as obtained in Example 52 (Catalysts F₅₁ -1 toF₅₁ -3) were each subjected to further treatment for reactivation underthe conditions as shown in Table 52. The thus reactivated catalyst wereeach reused for continuous partial combustion under the same conditionsas shown in Table 48. The results are shown in Table 52, from which itis understood that the catalysts reactivated in three steps are morerecovered in catalytic activity than the catalyst reactivated in twosteps.

                  Table 52                                                        ______________________________________                                        Catalyst        G.sub.52 -1                                                                            G.sub.52 -2                                                                              G.sub.52 -3                               Catalyst used   F.sub.51 -1                                                                            F.sub.51 -2                                                                              F.sub.51 -3                               ______________________________________                                        Condi-  Reactivating                                                                              H.sub.2  H.sub.2 :H.sub.2 O                                                                     H.sub.2 O:N.sub.2                       tions   agent                (1:1 by  (3:1 by                                 of                           mol)     mol)                                    treat-                                                                        ment                                                                          for     Temperature 600      600      650                                     reacti- (°C.)                                                          vation                                                                                Pressure    6.0      6.0      6.0                                             (ata)                                                                         Time (hrs)  6.0      6.0      12.0                                            Post-treat- --       --       --                                              ment                                                                  Elimina-                                                                              Carbo-      86       87       100                                     tion per-                                                                             naceous                                                               centage materials                                                             of                                                                            poisonous                                                                             Sulfurous   98       98       99                                      materials                                                                             materials                                                             (%)                                                                           Specific surface area                                                                         35       33         38                                        (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                            92       95         89                                        required (ml)                                                                 ______________________________________                                    

EXAMPLE 54

The reactivated catalysts as obtained in Examples 51 and 53 (CatalystsE₅₀ -1 and G₅₂ -3) were each reused for continuous partial combustionunder the same conditions as shown in Table 48. As the result, it wasrecognized that the reactivated catalysts show the same tendency as afreshly prepared catalyst (Catalyst A₄₉) in depression of the catalyticactivity.

EXAMPLE 55

A catalyst comprising 1.0% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter as a carrier material(hereinafter referred to as "Catalyst A₅₄ ") (290 ml) was charged into atubular reactor of 1 inch in diameter, and a gaseous mixture comprisingmethanol (content of sulfur, 5 ppm) and air was fed therein to effectcontinuously partial combustion for 300 hours under the conditions asshown in Table 53.

                  Table 53                                                        ______________________________________                                        Temperature of                                                                             at inlet    280° C.                                       reactor      at outlet   700° C.                                       Space velocity       17500 hr.sup.-1                                          Ratio of air/methanol                                                                              2.40 (by mol)                                            Pressure             1 atm.                                                                        (absolute)                                               ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₅₄ ") was treated under the conditions as shown in Table 54for reactivation. The reactivated catalyst was reused in partialcombustion reaction under the same conditions as mentioned above. Theresults are shown in Table 54.

As seen from Table 54, the reactivation treatment with hydrogen orhydrogen-steam is extremely effective for elimination of carbonaceousmaterials, but removal of sulfurous materials is insufficient and thedispersibility can be hardly recovered so that recovery of the catalyticactivity is scarcely observed. In the case of treatment with aninorganic alkaline substance at room temperature for a long time,elimination of sulfurous materials and recovery of the dispersibilityare good, but recovery of the catalytic activity is insufficient.Treatment with an inorganic alkaline substance under heating is provedto be effective for recovery of the catalytic activity. In treatmentwith a reducing substance, elimination of sulfurous materials is hardlyattained. However, there is a tendency to recovery of the catalyticactivity.

                                      Table 54                                    __________________________________________________________________________                       Reactivated                                                Catalyst     A.sub.54                                                                         B.sub.54                                                                         C.sub.54 -1                                                                       C.sub.54 -2                                                                        D.sub.54 -1                                                                       D.sub.54 -2                                                                       D.sub.54 -3                                                                       D.sub.54 -4                                                                        D.sub.54 -5                                                                        D.sub.54 -6                                                                       D.sub.54 -7                                                                        D.sub.54           __________________________________________________________________________                                                               -8                       Reactivating                                                                         -- -- H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 0.375N                                                                            0.375N                                                                            0.375N                                                                            0.375N                                                                             0.375N                                                                             0.4%                                                                              0.3% 1.0%               Condi-                                                                              agent            (1:1 by                                                                            NaOH                                                                              NaOH                                                                              NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       Hydra-                                                                            Glucose                                                                            Formal-            tions                  mol)                       zine     dehyde             of    Temperature                                                                          -- -- 600 600  30  50  100 100  100  20  20   60                 treat-                                                                              (°C.)                                                            ment                                                                          for   Pressure                                                                             -- -- 6.0 6.0  1.0 1.0 1.0 1.0  1.0  1.0 1.0  1.0                reacti-                                                                             (ata)                                                                   vation                                                                              Time (hrs)                                                                           -- -- 6.0 6.0  10.0                                                                              6.0 1.5 3.0  3.0  3.0 3.0  3.0                      Post-treat-                                                                          -- -- --  --   Water washing: 100° C., 2                                                                    Water washing:                    ment                  Drying: 100° C., 16 hrs.                                                                     75° C., 3 hrs.                                                         Drying: 100° C.,                                                       16 hrs.                     Elimina-                                                                      tion per-                                                                           Carbo- -- -- 100 100  41  43  44  43   40   0   0    0                  centage                                                                             naceous                                                                 of    materials                                                               poisonous                                                                           Sulfurous                                                                            -- -- 31  32   72  78  95  85   84   72  50   68                 materials                                                                           materials                                                               (%)                                                                           Specific surface area                                                                      43 13 13  17    20 24  29  28   26   22  23   23                 (m.sup.2 /g-Ru)                                                               Amount of catalyst                                                                         85 -- --  --   --  150 115 120  127  163 161  160                required (ml)                                                                 __________________________________________________________________________

EXAMPLE 56

A catalyst comprising 2.0% of platinum deposited on spheroidal particlesof alumina of 4 mm in diameter as a carrier material (hereinafterreferred to as "Catalyst A₅₆ ") (290 ml) was charged into a tubularreactor of 1 inch in diameter, and a gaseous mixture comprising methaneand air was fed therein to effect continuously partial combustion for300 hours under the conditions as shown in Table 55.

                  Table 55                                                        ______________________________________                                        Temperature of                                                                             at inlet      310° C.                                     reactor      at outlet     700° C.                                     Space velocity         17500 hr.sup.-1                                        Ratio of air/methane   2.37 (by mol)                                          Pressure               1 atm.                                                                        (absolute)                                             ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₅₆ ") was treated under the conditions as shown in Table 56for reactivation. The reactivated catalyst was reused in partialcombustion reaction under the same conditions as mentioned above. Theresults are shown in Table 56.

As seen from Table 56, the reactivation treatment with hydrogen orhydrogen-steam is extremely effective for elimination of carbonaceousmaterials, but removal of sulfurous materials is insufficient and thedispersibility can be hardly recovered so that recovery of the catalyticactivity is scarcely observed. In the case of treatment with aninorganic alkaline substance at room temperature, elimination ofsulfurous materials and recovery of the dispersibility are relativelygood when the treating time is long, but recovery of the catalyticactivity is insufficient. Treatment with an inorganic alkaline substanceunder heating is proved to be effective for recovery of the catalyticactivity. In treatment with a reducing substance, elimination ofsulfurous material is good, but removal of carbonaceous materials ishardly attained. However, there is a tendency to recovery of thecatalytic activity.

                                      Table 56                                    __________________________________________________________________________                       Reactivated                                                Catalyst     A.sub.56                                                                         B.sub.56                                                                         C.sub.56 -1                                                                       C.sub.56 -2                                                                        D.sub.56 -1                                                                       D.sub.56 -2                                                                       D.sub.56 -3                                                                       D.sub.56 -4                                                                        D.sub.56 -5                                                                        D.sub.56 -6                                                                        D.sub.56 -7                                                                       D.sub.56           __________________________________________________________________________                                                               -8                 Condi-                                                                              Reactivating H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 0.375N                                                                            0.375N                                                                            0.375N                                                                            0.375N                                                                             0.375N                                                                             0.4% 0.3%                                                                              1.0%               tions agent  -- --     (1:1 by                                                                            NaOH                                                                              NaOH                                                                              NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       Hydra-                                                                             Glu-                                                                              Form-              of                     mol)                       zine cose                                                                              alde-              treat-                                                     hyde               ment                                                                          for   Temperature                                                             reacti-                                                                             (°C.)                                                                         -- -- 600 600  30  50  100 100  100  20   20  60                 vation                                                                              Pressure                                                                      (ata)  -- -- 6.0 6.0  1.0 1.0 1.0 1.0  1.0  1.0  1.0 1.0                      Time (hrs)                                                                           -- -- 6.0 6.0  10.0                                                                              6.0 1.5 3.0  3.0  3.0  3.0 3.0                      Post-treat-                                 Water                             ment   -- -- --  --   Water washing: 100° C., 2                                                                    washing: 75° C.,                                                       3 hrs.                                                  Drying: 100° C., 16 hrs.                                                                     Drying: 100° C.,                                                       16 hrs.                     Elimina-                                                                            Carbo-                                                                  tion per-                                                                           naceous                                                                              -- -- 75  76   40  42  44  43   40    0    0   0                 centage                                                                             materials                                                               of                                                                            poisonous                                                                           Sulfurous                                                               materials                                                                           materials                                                                            -- -- 22  27   72  79  94  86   86   74   52  70                 (%)                                                                           Specific surface area                                                         (m.sup.2 /g-Ru)                                                                            41 15 15  15   22  24  29  28   27   23   24  24                 Amount of catalyst                                                            required (ml)                                                                              48 -- --  --   --  87  73  75   77   90   94  92                 __________________________________________________________________________

EXAMPLE 57

A catalyst comprising 2.0% of ruthenium deposited on spheroidalparticles of alumina of 4 mm in diameter as a carrier material(hereinafter referred to as "Catalyst A₅₈ ") (350 ml) was charged into atubular reactor of 1 inch in diameter, and a gaseous mixture comprisingnaphtha (content of sulfur, 2 ppm; final boiling point, 108° C.) and airwas fed therein to effect continuous partial combustion for 200 hoursunder the conditions as shown in Table 57.

                  Table 57                                                        ______________________________________                                        Temperature of                                                                             at inlet    350° C.                                       reactor      at outlet   900° C.                                       Pressure             1 atm.                                                                        (absolute)                                               Ratio of air/naphtha 14.0 (by mol)                                            Space velocity       17500 cm hr.sup.-1                                       ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as"Catalyst B₅₈ ") was treated under the conditions as shown in Table 58for reactivation. The reactivated catalyst was reused in partialcombustion reaction under the same conditions as mentioned above. Theresults are shown in Table 58.

As seen from Table 58, the reactivation treatment with a gaseousmaterial is effective for elimination of carbonaceous materials, butremoval of sulfurous materials is insufficient and the dispersibilitycan be hardly recovered so that recovery of the catalytic activity isscarcely observed. In the case of treatment with an inorganic alkalinesubstance at room temperature for a long time, elimination of sulfurousmaterials and recovery of the dispersibility are good, but recovery ofthe catalytic activity is not well recognized (Catalyst D₅₈ -1). Whentreated with an inorganic alkaline substance under heating, thecatalytic activity is highly recovered (Catalysts D₅₈ -2to D₅₈ -5).Treatment with an aqueous solution of hydrazine or the like is effectivein elimination of sulfurous materials but not in elimination ofcarbonaceous materials. However, a tendency to recovery of the catalyticactivity is recognized (Catalysts D₅₈ -6 to D₅₈ -8).

                                      Table 58                                    __________________________________________________________________________                         Reactivated                                              Catalyst      A.sub.58                                                                         B.sub.58                                                                          C.sub.58 -1                                                                      C.sub.58 -2                                                                        D.sub.58 -1                                                                       D.sub.58 -2                                                                       D.sub.58 -3                                                                       D.sub.58 -4                                                                        D.sub.58 -5                                                                        D.sub.58 -6                                                                       D.sub.58 -7                                                                      D.sub.58            __________________________________________________________________________                                                              -8                  Condi-                                                                             Reactivating    H.sub.2                                                                          H.sub.2 :H.sub.2 O                                                                 0.375N                                                                            0.375N                                                                            0.375N                                                                            0.375N                                                                             0.375N                                                                             0.4%                                                                              0.3%                                                                             1.0%                tions                                                                              agent    -- --     (1:1 by                                                                            NaOH                                                                              NaOH                                                                              NaOH                                                                              Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                       Hydra-                                                                            Glu-                                                                             Form-               of                      mol)                       zine                                                                              cose                                                                             alde-               treat-                                                    hyde                ment                                                                          for  Temperature                                                                            -- --  600                                                                              600  30  50  100 100  100  20  20 60                  reacti-                                                                            (°C.)                                                             vation                                                                             Pressure -- --  6.0                                                                              6.0  1.0 1.0 1.0 1.0  1.0  1.0 1.0                                                                              1.0                      (ata)                                                                         Time (hrs)                                                                             -- --  6.0                                                                              6.0  10.0                                                                              6.0 1.5 3.0  3.0  3.0 3.0                                                                              3.0                  Post-treat-                 Water washing: 100° C., 2                                                                    Water washing:             ment                                               75° C., 3 hrs.                    -- --  -- --   Drying: 100° C., 16                                                                          Drying: 100°                                                           C., 16 hrs.                Elimina-                                                                           Carbo-                                                                   tion per-                                                                          naceous  -- --  100                                                                              100  48  51  52  53   51   0   0  0                   centage                                                                            materials                                                                of                                                                            poisonous                                                                          Sulfurous                                                                materials                                                                          materials                                                                              -- --  23 25   70  80  93  90   91   70  51 69                  (%)                                                                           Specific surface area                                                         (m.sup.2 /g-Ru)                                                                             42 11  11 14   17  22  28  29   27   26  27 27                  Amount of catalyst                                                            required (ml) 80 --  -- --   --  156 118 115  120  155 156                                                                              155                 __________________________________________________________________________

What is claimed is:
 1. A method for reactivation of a platinum groupmetal catalyst which comprises contacting a platinum group metalcatalyst lowered in the catalytic activity as the result of having beenused for hydro-cracking of hydrocarbons or alkanols with an aqueoussolution of an inorganic alkaline compound of alkali metal or alkalineearth metal or mixtures thereof in a concentration of 0.001 to 10 N at atemperature of 5° to 250° C. until the catalytic activity of thecatalyst is substantially recovered.
 2. The method according to claim 1,wherein the inorganic alkaline compound is a member selected from thegroup consisting of hydroxides, carbonates, nitrates and sulfates ofsodium, potassium, calcium, magnesium, barium and stronthium.
 3. Themethod according to claim 1, followed by treatment with at least one ofhydrogen, oxygen and steam at a temperature of 350° to 750° C. under apressure of 1 to 50 atm. (absolute) until poisonous materials depositedon the catalyst are eliminated.
 4. The method according to claim 1,wherein the catalyst is previously treated with at least one ofhydrogen, oxygen and steam at a temperature of 350° to 750° C. under apressure of 1 to 10 atm. (absolute) until poisonous materials depositedon the catalyst are eliminated.
 5. The method according to claim 1,wherein the catalyst is previously contacted with an aqueous solution ofa reducing substance in a concentration of 0.01 to 10% by weight at atemperature of 5° to 250° C. for a period of 3 minutes to 80 hours andthen treated with at least one of hydrogen, oxygen and steam at atemperature of 350° to 750° C. under a pressure of 1 to 50 atm.(absolute) until poisonous materials deposited on the catalyst areeliminated.
 6. A method for reactivation of a platinum group metalcatalyst which comprises contacting a platinum group metal catalystlowered in the catalytic activity as the result of having been used forhydro-cracking of hydrocarbons or alkanols with an aqueous solution of areducing substance in a concentration of 0.01 to 10% by weight at atemperature of 5° to 250° C. until the catalytic activity of thecatalyst is substantially recovered.
 7. The method according to claim 6,wherein the reducing substance is a member selected from the groupconsisting of hydrazine, formaldehyde, sodium borohydride, lithiumaluminum hydride, sodium tartrate, potassium tartrate, sodium potassiumtartrate, calcium tartrate, sodium hydrogen tartrate, sodium formate,potassium formate, calcium formate and glucose.
 8. The method accordingto claim 6, followed by treatment with at least one of hydrogen, oxygenand steam at a temperature of 350° to 750° C. under a pressure of 1 to50 atm. (absolute) until poisonous materials deposited on the catalystare eliminated.
 9. The method according to claim 6, wherein the catalystis previously treated with at least one of hydrogen, oxygen and steam ata temperature of 350° to 750° C. under a pressure of 1 to 50 atm.(absolute) until poisonous materials deposited on the catalyst areeliminated.
 10. The method according to claim 6, wherein the catalyst ispreviously contacted with an aqueous solution of an inorganic alkalinecompound of an alkali metal or alkaline earth metal or mixtures thereofin a concentration of 0.001 to 10 N at a temperature of 5° to 250° C.for a period of 3 minutes to 80 hours and then treated with at least oneof hydrogen, oxygen and steam at a temperature of 350° to 750° C. undera pressure of 1 to 50 atm. (absolute) until poisonous materials,deposited on the catalyst are eliminated.
 11. A method for reactivationof a platinum group metal catalyst which comprises contacting a platinumgroup metal catalyst lowered in the catalytic activity as the result ofhaving been used for hydro-cracking of hydrocarbons or alkanols with anaqueous solution or a reducing substance in a concentration of 0.01 to10% by weight at a temperature of 5° to 250° C. for a period of 3minutes to 80 hours and then treating the catalyst with an aqueoussolution of an inorganic alkaline compound of alkali metal or alkalineearth metal or mixtures thereof in a concentration of 0.001 to 10 N at atemperature of 5° to 240° C. until the catalytic activity of thecatalyst is substantially recovered.